Use PImpl idiom to hide Format and Filter headers from users of Vecs, FilterVecs...

Use PImpl idiom to hide Format and Filter headers from users of Vecs, FilterVecs. (#854)

* use pimpl to hide vec implementation of formats.

* use PIMPL for filter_vecs.

* sort vecs and filter_vecs include files.

* workaround memory leak issues with pimpl vecs, filter_vecs.

with some compilers sanitize address and valgrind reported errors.
The number of errors varied with compiler/platform.
Valgrind and sanitize address found different errors as well.
MacOS with clang 13 ran error free.
Linux with gcc9 and clang 10 showed multiple errors.
The errors detected were related to the destruction of the Format
and Filter instances.

* move ctors/dtors back to h files.

* catch nuke_format up with vecs.