FlatHub uses org.kicad.KiCad and everyone else uses org.kicad.kicad,
which leads to two entries in the Gnome Software search list for kicad.
To unify this into one entry, have each just provide the other app ID to
link them together.
* Switch to using org.kicad.kicad as the main app ID
* Move the appstream file to a metainfo file
* Rename all metadata files to use the reverse DNS scheme
* Add header matching to mime type files where possible
* Add a mime type for gerber job files
* Add a QA test that verifies all the linux metadata files and
run it in CI
* Update the visible names in the launcher entries to be more
consistent with the internal visible names
* Update various strings and items in the metainfo file so they
are more descriptive and easier to read
The BuildSteps folder now contains the CMake scripts that are
called during the build process as individual stages, while
the root CMakeModules directory contains the CMake files used
during the configuration phase.
