[matter] pass a full Spec object to Binary PMS commit() methods

This makes possible to use the extra pieces of information in order
to implement more complex features
[matter] fix build-args parameter handling (remove unwanted comma)
[matter] call _emerge.actions.{adjust_configs,apply_priorities} on every Scheduler run

This is actually required to make -B and -b emerge options working as intended
[matter] add support for committing tbz2s directly.

When Portage is asked to only build a package (with -B), Matter
should locate the generated tbz2 and add it to the binary repository.
This also makes possible to track injected packages and have them
automatically bumped.
[matter] add another example file
[matter] add build-only parameter support, wrapping --buildpkgonly + --buildpkg
[matter] add support for external .spec parsers
[matter] add new drop-old-injected argument support.

This will make possible to fully support automated injected packages
bump.