[12420] Add support for XP-Gain disabling

Add CONDITION_XP_USER to be able to check if a player has XP-Gain enabled or disabled
Add SCRIPT_COMMAND_XP_USER to enable/disable XP-Gain for a player

Signed-off-by: Schmoozerd <schmoozerd@scriptdev2.com>
[12421] Implement CONDITION_GENDER Thanks to crackm for testing