Implement .rt and args parsing, move test scene

Implement .rt and args parsing, move test scene

Add rt_grammar and rt_parsing_table as they describe the grammar used to
parse the .rt file. Their contents are available to he program through
the file parsing_info.h where they are encoded (using xxd -i).

The test_scene is added for testing as the "default scene" had to be
erased from main for parsing to be enabled.

Other changes involve the parsing implementation directly.