Updated JSON conversion

[Bob]

as per: XF 2.1 - Welcome to XenForo 2.1 / Assorted improvements

Traditionally we have always used PHP's built-in serialization features as a way to encode data arrays as strings for database storage. Although there are still some benefits to using serialization, we have updated most of our schema to use JSON going forward.

From a development point of view, we would recommend developers follow suit and move their existing data to JSON if they haven't already and they are able to.

I have updated the AMS schema to use JSON going forward as well.