Item DB overhaul

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>
Removed redundant item_db2_re.sql

- Both databases have the same format now.
- Special thanks to Ind.

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>
Added item_db2.sql conversion script to the new structure

- For those using a SQL item_db2, I provided a convenience script to
  update to the new structure without having to delete and re-import
  your data.
- The script requires at least MySQL 5.0 (tested on MySQL 5.6) and works
  for both Pre-Renewal and Renewal tables. If you're running an older
  version (Oracle advises to upgrade for security reasons by the way!),
  open the upgrade script in your text editor, and you'll find
  the queries you can run manually instead.
- Special thanks to Ind.

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