Also shortens some related code and adds more parameters to string.split.

Changes:
  * Indentation with tabs by default.
  * Array keys dumped without "[i] = " prefix.
  * String keys that are valid identifiers aren't enclosed in '[""]'.
  * Basic support for multiple references (as specified in the comment).

Changes:
  * Add comments to explain the dumping code
  * Add support for dumping values of any type (as '<' <type> '>')
  * Add support for tables as keys in dump2()
  * Make dump2() return it's result (like dump()) rather than printing it
  * Simplify and optimize function serialization via serialize()

Add engine.gettext() and remove gettext() calls in guiFormspecMenu.cpp