Changed to Data Providers and added buy/sell confirmations.
CanPlayerBuy/Sell and update checker fixes.

CanPlayerBuy can now either be a boolean for people too silly to use or
don't need to use callbacks.
Added CanPlayerSell which acts the same as CanPlayerBuy.
Fixed update checker erroring when GitHub servers return bad data.
Added missing validation. Added provider checks.
Moved data loading to the timer, should fix sync issues.
Clamped sending points to positive integers.

No more sending other players negative amounts of points.
Added a CATEGORY.Order field
Added category order support

Categories should sort on category, then name. That way if none of the categories are set, they'll still behave the same.
Added support for CATEGORY.Order. Default order is 0. The lower an order is, the farther left it will be. After sorting by order, it will sort by name. This also fixes what I believe is a bug where categories are sorted Z-A.
Merge pull request #46 from NullEntity/master

Added support for CATEGORY.Order and fixed categories sorting Z-A
Added check for valid player before loading data. Happens when someone instantly leaves the server after connecting.
fix reported by nextem