compile in gpsbabel translations and map on non mac unix distribution… (#622)

compile in gpsbabel translations and map on non mac unix distribution… (#622)

* compile in gpsbabel translations and map on non mac unix distributions by default.

This eliminates the need to install gpsbabelfe_*.qm, gpsbabel_*.qm and
gmapbase.html on the system.
Note that the Qt supplied translations must still be installed on the system.
The Qt translations may be in a package like qttranslations5-l10n or
qt5-qttranslations.

* simplify optional resources using std methods.

* discuss dependencies in INSTALL.