TRIBS-134 IAC FTSearch on all fields combined into one

TRIBS-134 IAC FTSearch Fix null concatenation. Add test for metadata search.

TRIBS-134 IAC FTSearch Modify index to use coalesce. Fix for TRIBS-167.
Merge pull request #75 from ministryofjustice/iac-search

TRIBS-134 IAC FTSearch on all fields combined into one