[FTS] add synonym support

Spec out and design capability for custom synonym analyzer.  Possibly something like an Admin provides a two column word/lookup list (twisting the meaning of the term here, I'm sure) mapping one word to the other.

e.g. mywords.csv
happy,glad
grumpy,sad

Allow use of this list in a built-in analyzer to understand the lookup. e.g. Search for happy, will behind the scenes search for glad and return results for glad.

All words should be a single language and that language defined in custom analyzer creation.

p.s.  Could help enable some interesting examples, such as sentiment analysis.