Fix#67
Spawn table updated with merchant_min_level and merchant_max_level, extends to spawns, widgets, objects and signs.
Restricts the min level required and a max level cap on a player able to use the merchant (buy/sell/display)
/spawn set merchant_min_level x
/spawn set merchant_max_level x
This will fix#131 requirement. disable_sounds will be made to more globally disable a spawns sounds that might otherwise be defaults.
We can either later on decide to use the widget open/close sound or maybe have another sound file field that allows a different value than mariner bell.
This update also allows signs to check expansion flags and fixes widgets pulling the wrong field
