Added translation_parser_version field to the sites table so that different sites can use different HTML parsers.  This allows us to lock parsing in place for existing apps whilst still improving the parser for future apps.  The default value for new sites is version 2 (and will be changed as parser is improved) but existing sites default to null which just uses the original parsing class.
Merge branch 'master' of https://github.com/shannah/swete