Add more tags to the list of things the decompiler can handle. This
required some changes to track the containing object class in the
DecompileCtx, since some objects use the same tag names.
The improved support means we can test the decompiler on most of the
test suite. Any new test samples will by default be tested to ensure the
decompiler produces the original blueprint file.
Also, updated the decompiler to always use double quotes.
Load the outputs of the tests in Gtk.Builder and make sure they work.
Some of them don't and need to be fixed. Others will require a bit more
work to set up callbacks, templates, etc.
