add npc area size field.
Add script command to set npc click/activate instance.

New script command: setnpcdistance N
Where N is distance in tiles from where npc can be clicked.
Add setnpcdistance into docs.
Fix script error termination if already running script continue from very far npc.

Note for Haruna: possible it may add side effects. Need check.
Add getnpcdir and setnpcdir functions.
Add script command getnpcclass.
Fix incorrect memory access in script command getareausers.
Extend script command getareausers.
Add function what call OnUntouch event.
Add function what called if player leave npc area.
If player left npc, call onUnTouch event.
Add OnUnTouch event/label into scripts documentation.
Merge pull request #409 from 4144/npcdistance

Extend npc/script commands
HPM Hooks Update

Signed-off-by: HerculesWSAPI <Hercules@efficiently.awesome>
Move check is item usable or not to separate method.

New method: itemdb_is_item_usable
Can be used as: itemdb->is_item_usable(item)
Update HPM hooks.