Refactor Metadata tables.

Metadata is now a single string in both the TU and TUVs.
Change the way the Translation Memory size is being calculated in the home page. It's now done using a query.
Add pages.xml entry for the Trans Memory admin home page.
Fix handling of metadata
Check metadataType in setMetadata
Implement 'merging' of existing TUs when importing TMX files.
Fix issues when clearing a translation memory.
Add JUnit annotations
Add DTD validation for TMX files
Add TMX export option in the TM home page.

Change verbiage in the TM home page.
Add delete feature from translation memories.
Merge branch 'tm-import' into tmx-dashboard