Factor string normalization functions out of Utils.

This introduces a StringNormalizer service and replaces
any use of the static normalization functions in Utils.

Change-Id: Ieeba2470dccf797b37243355ddcb2ccf5e5b18c0
Move search key generation to TermSqlIndex.

Search key generation is specific to the storage/search engine.
The code was misplaced in the Term class, which required awkward
hacks to get access to the required helper classes / servces.

Change-Id: I8fd9eba0999b1bfcb69dba0bd84723e491f1e012