Syntax highlighting improvement for library/modules.
Make folding a bit more robust.

This is the start of improving folding for when error handling
starts being added.
Fix formatting.
Pratt-style expression parse tree.
Merge pull request #38 from BarAgent/statements

Pratt-style expression parse tree.
Remove unused properties from new file actions.
Fix definitions of constants and variables.
Make body & constituents non-private.

These should not be private as without that, we lose ordering and
operating on the PSI structure for things like refactorings and
surrounders becomes much more difficult / error prone.
Rename file icons, add Retina versions.

Thanks Seyi for the Retina versions!
Fix definitions of slots
Define unique strings as tokens

Fix #40
Remove import of removed class.
Support method separators.