Add framework for private parking

This is a highly configurable addon for enabling private parking.

Config options are:

//List of cities where private parking is available (empty or unset means all cities)
pp_cities_whitelist = [];

//whether or not to show map markers for private parking locations
pp_markers_enabled = true;

//shape, type, color, size, text (for map markers, if enabled)
pp_markers_properties = ["ICON", "mil_dot", "ColorKhaki", [1.2,1.2], "Parking"];

//number of seconds to wait (after parking a vehicle) before it can be retrieved (0 = no wait)
pp_retrieve_wait = 0;

//amount of money to charge player for retrieving a vehicle from parking (0 = no charge)
pp_retrieve_cost = 0;

//maximum number of vehicles that a player can park (0 = no limit)
pp_max_player_vehicles = 0;

//List of class names for vehicles that are not allowed to be parked
pp_disallowed_vehicle_classes = [];
Fix tabs in private parking addon
Enable persistence for private parking
Parking fixes for safe position, and UI scrollbar

For some reason the RscListBox UI dialogs, get their scrollbar messed up
if you change the height of the dialog after it has already been created.

Also, add a fix for placing vehicles safely when retrieving them from the
parking.
More tab/space fixes
Restrict parking locations in Altis
Merge pull request #31 from micovery/private_parking

Private parking