Update to Button, removed feature, added 2 funcs

Button: Removed vehicle attachment feature, it never worked as intended
and was overall lazily coded. A better example can be found inside the
vehicle interaction code of Scavenge and Survive.

Added two new functions, GetPlayerAngleToButton and
GetButtonAngleToPlayer to easily return offset angles between players
and buttons, useful for creating buttons that can only be activated from
one side or sector.

Improved player area detection to exempt spectating players from area
checks. This way the system can be used with administration systems
where under-cover spectating is vital. The player won't see options to
give an item for instance when another player is spectating them.