Item DB revamp

http://hercules.ws/board/topic/2954-item-db-file-structure-overhaul

- 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 in the tools directory (and a link
  to the web-based version of the same script canbe found in the above
  forum topic)
- All of this was made possible thanks to Ind, Yommy.

Signed-off-by: Haru <haru@dotalux.com>
Updated db2sql plugin for the needs of the new itemdb

May be used as ./map-server --db2sql or by typing "server tools db2sql" within map-server console parse.
Special Thanks to Haruna.

Signed-off-by: shennetsind <ind@henn.et>
Added Inheritance support for item_db2

- If an item is marked as Inherit: true in item_db2, and it already
  exists, in item_db, then any unspecified fields are taken from the
  item_db entry rather than using their default values.
- Special thanks to Ind.

Signed-off-by: Haru <haru@dotalux.com>