Added support for USR version 5 and 6 and corrected USR version 4 support. (#268)

Added support for USR version 5 and 6 and corrected USR version 4 support. (#268)

* Minor changes to address GCC 7.3.0 warnings generated by flag -Wunused-but-set-variable.

Moved declaraions/initialization of rp_backup and era inside #ifdef _NL_CURRENT conditionals.

* Added { ... } to for at the end of zip64local_SearchCentralDir() so that if-break statements inside for loop.

* Removed declaration and commented out references to startlat, startlon, and starttime in fit_parse_data() due to GCC 7.3.0 warning from
flag -Wunused-but-set-variable.

* Added initial support for Lowrance USR 5 and 6 formats.

* Significant changes to handle multiple USR4 versions and add USR5 and USR6 support.

* Remove extraneous debug NL when no debug specified.

* Updated USR4 reference file because of increased accuracy in converting lat/log values.

* Documentation on some ICON mappings.

* Added USR5 and USR6 to validation checks.

* Added reference files for USR5 and USR6 formats.

* Cleaned up some debug output.

* Continued work to consolidate all Lowrance USR processing into a single file.

* Eliminated lowranceusr4.cc and restuctured testing to include USR4, USR5, and USR6 formats.

* Changes associated with adding support for USR 5 and USR 6.

* Eliminated lowranceusr4.cc from build.

* Changed default Output USR Version from 4 to 2 for backward compatibilty.

* Removed USR 4 section from documentation.

* Initial update of XMLDOC for updated data formats.

* iMinor updates to parse_routes.  Added correct v4 and v5 GPX reference files.

* Documentation updates to reflect new capabilities.

* Added Route element information to document and minor code changes to match.

* Doc refinement with rewrite.

* Corrections to USR 4 output.

* Update to correct v4 gpx file.

* Checkin correct v5 gpx file.

* Removed errant NL when no debug specified.

* Resolved conflicts

* Missed this update.

* Revert "Minor changes to address GCC 7.3.0 warnings generated by flag -Wunused-but-set-variable."
at the request of tsteven4 as they have nothing to do with the expanded support.

This reverts commit fb93a19b740edae4dde3b6dcd0546f344122f70d.

* Revert "Added { ... } to for at the end of zip64local_SearchCentralDir() so that if-break statements inside for loop."
at the request of tsteven4 as they have nothing to do with the expanded support.

This reverts commit 189bbe6ea664829412c70079e9ddb9555062a12f.

* Revert "Removed declaration and commented out references to startlat, startlon, and starttime in fit_parse_data() due to GCC 7.3.0 warning from"
at the request of tsteven4 as they have nothing to do with the expanded support.

This reverts commit cc618336888c5cdb8adef87f72026a8c24eff7e8.

* Updated to remove lowranceusr4.cc per suggestion from tsteven4 to support cmake/XCLion.

* Per suggestions from tsteven4
    - deleted define SECSTORADIANS as it was not used
    - ran astylerc

* Replaced use of NULL with nullptr per tsteven4 suggestion.

* Added URLs for reference information.

* Adopted tsteven4 recommendation on eliminating compiler warning.

* Corrections to Waypoint and Trail documentation for USR 4, 5, and 6 formats.

* Address Codacy flagged issues.

* Address Codacy flagged issues.

* Address additional Codact flaged issues.

* Changed DEGREESTORADIANS define from hardcoded value to use (M_PI/180.0)

* Removed Copyright protected material and replaced with authored comments.

* Corrected altitude/depth retension coverting USR4/5/6 to USR2/3

* Added mapping of USR4/5/6 ICON numbers to text to support output to USR 2/3 format.

* Corrected generation of USR4 data file.

* Check for NULL format specific when converting USR 2/3 (colorless) to USR4 (color coded) ICONs.

* Added cases where USR 2/3 embeds color in shortname.

* Corrections to ICON translation from USR v2/3 to USR 4.

* Cleanup USR 2/3 parsing debug.

* Adopted modificatins to USR 4/5/6 time interpretation per suggestion from tsteven4.

* Adopted modificatins to USR 4/5/6 time interpretation per suggestion from tsteven4.

* Changed file header parsing back to int16 for USR format as found sample file with a stream version other than 0.  Assume this
is true for ALL USR formats until determine otherwise.

* Updated reference files after corrections to altitude and time conversion.

* Check for both "nan" and "-nan" to address compiler differences.

* Use -options instead of --options to avoid osx OS issues.

* Set altitude to "unknown_alt" when creating Waypoints from Event ICONs.
Updated reference files to encorporate "unknown_alt" change.
Corrected mis-spelling of "green"

* Change cut options from --compliment to legacy explict field list for OSX OS support.

* Applied codex patch from tsteven4 - thank you.

* Corrected interpretation of elevation in USR2/3.

* Corrected reference files and test script with changes to elevation interpretation.

* More conversions to QString conventions.
Minor correction to trail attribute parsing.

* Editorial cleanup.

* USRv6 uses trail data stream version 5 which employs int32 rather than char for attributes.

* Use invalid ICON value as method to detect HOOK2 generated USR 2/3 files.

* Cleanup time conversions.