Finish creation of the new EDL parser

Last year's project, titled "Data Buffers/Serialization", led to a complete
rewrite of the EDL (ENIGMA Development Language) parser. As it stands, the
parser can parse most of the EDL language, with some features which are
incomplete marked as "Unimplemented".

• The project would begin by finishing up the unimplemented features, and adding
  more test cases to the parser tests,
  to try and achieve maximal coverage.
• The issues mentioned in issue #2316
  would be fixed possibly by implementing a pass which walks the AST to modify
  it as per the issues mentioned.
• The parser would then be implemented into ENIGMA itself, by replacing calls
  to the old parser with calls to the new one. This would also involve writing
  routines to lower the AST into ENIGMA's data structures.

Mentors: Josh, Greg
Difficulty: Medium/Hard
Expected size: 250h - 350h
Skills required: C++ fundamentals, compiler fundamentals