Item DB revamp [WORK IN PROGRESS]

DO NOT MERGE, this needs to be amended

- Item db was changed to libconfig format.
- This new format is larger than the original format, but it's less
  subject to conflicts when some items are edited and the file gets
  updated.
- It is no longer necessary to specify fields with no value, and only
  the actually used fields are specified.
- Items scripts (especially the long ones) are made more readable by
  splitting them into multiple lines, with proper indentation.
- a converter perl script is provided -- TODO: Maybe provide a web based
  version?
- TODO: Forum post with some explanation would be good - add link here
- Made possible thanks to Ind, Yommy.