LuaPrinter.hx prettyprint patch

A pack of changes since I failed to fork correctly and instead got a local unmergeable branch.
- Empty TBlocks no longer generate an `end` statement.
- Indentation is now incremented/decremented before/after expression printing, as opposed to doing so in TBlock. This produces more consistent results in terms of structure.
- Switch code is now cleaner, with case-blocks residing on indented lines.
- Cleaned up if-then-else block generation slightly. Now omits double parenthesis, in particular.
- Fixed do-while loops to convert into Lua' repeat-until loops.
- Slightly changed constructor generation to both create a table and set it's metatable at once.
I think that's all.