Added TermsLookup class in utils and possiblity to add it to TermsFilter
Took the information from here and added them to the new classes.
http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/query-dsl-terms-filter.html#_terms_lookup_mechanism
Merge pull request #448 from julianhille/feature/added_missing_terms_lookup_filter

Added TermsLookup class in utils and possiblity to add it to TermsFilter