Takes the time required to do initial database creation down from
16 to 0.2 seconds on the Raspberry Pi.

- Made the current charge being saved.
- Added script binds:
  - chr_set_special_recharge_speed
  - chr_get_special_recharge_speed
  - chr_set_special_mana
  - chr_get_special_mana
  - get_special_info
- Added special info lua class. Functions:
  - name
  - needed_mana
  - rechargeable
  - on_use
  - on_recharged
  - category

Further the engine no longer sets charge to 0 after using of specials
this allows more flexbilillity (like failing specials).

Changes on the xml database:
- recharge renamed to rechargeable (needed by client and server)
- needed - the needed mana to trigger a special (server only)
- rechargespeed - the defailt recharge speed in mana per tick (server only)
- target - the type of target (either being or point) (server and client)

I also made the lua engine pushing nil instead of a 0 light userdata when
the pointer was 0.

Database update needed.

Change is tested.

Mana-Mantis: #167, #156

Reviewed-by: bjorn.

Forgot this in 1afbfb7e5fb5c133924ed8d376c6064575fc1c36.

Reviewed-by: Bertram, Ablu.

Due to a wrong primary key, which covered only the state name, it was
impossible to use the same state name on different maps. This has now
been fixed.

Another problem was that the map variables were being included in the
global variables, because the related database query did not filter on
the map_id column properly. While fixing that, the map_id column now
allows explicitly marking a state variable as global (with the value 0)
or system variables (with the value -1).

System variables are currently not accessible from scripts, but that
could be changed later.

Reviewed-by: Yohann Ferreira
Reviewed-by: Erik Schilling

Changed range of amount to unsigned int(10).
Sqlite update scripts is empty since no change was required here.

Reviewed-by: Bertram.

Conflicts:
	src/game-server/character.cpp
	src/scripting/lua.cpp

Version 15 was skipped, and we'll never go back. Renamed the 15_to_16
update scripts to 14_to_16 to avoid confusing everybody who wants to
update their DBs.

Reviewed-by: Yohann Ferreira