Fixed Bug#8469
-http://hercules.ws/board/tracker/issue-8469-issue417-refine-weapon-may-caused-server-to-crash/?gopid=24287#entry24287

Signed-off-by: malufett <malufett.eat.my.binaries@gmail.com>
Merge branch 'master' of https://github.com/HerculesWS/Hercules
Add struct item_data, mob_db and mob_data for plugins

http://hercules.ws/board/topic/7161-plugin-missing-hook-to-struct-item-data-and-mob-data/
Remove plugin data in item_data destruction.
Move mob_db deletion into separate function.
Remove plugin data in mob_db destruction.
Remove plugin data in mob_data destruction.
Add function for reading custom itemdb fields.

This functions called after reading normal fields and after
adding item to itemdb.
Update HPM hooks.