[TIMOB-7640] Add list of allowable property values to Titanium Mobile API documentation

As prompted by this (http://developer.appcelerator.com/question/132035/titanium-studio-strange-behaviour#answer-230216) developer Q & A, users are confused as to why they don't get content assist for the allowable values for properties in Titanium Mobile. Titanium Studio could show these values, if they were encoded in the JSCA file. Suggestion is to amend the TiDoc format to add in a list of allowable property values, and then at least augment the docs with values for the most commonly used properties. It might be that many properties share a common list of values, so perhaps references could be used to avoid duplication.