Add %_live%, %_cover% etc. for work relationships.
Add NEWS
Switch variable names and add ~workrelationship

which mimics the work relationship statement on the MB web site e.g.
`{live} {medley:medley including a} {partial} {instrumental} {cover}
recording of`
Handle i18n differently ...

... so that work relationship text can be translated as a phrase and not
as individual words.
Fix metadatabox sort order

Sort by displayed value not internal value.
Merge pull request #297 from Sophist-UK/sophist_fix_metadata_display_sort_order

Fix metadatabox sort order
Remove ~workrelationship stuff.
Merge pull request #285 from Sophist-UK/sophist_add_work_relationship_variables

Add %_performance_live%, %_performance_cover% etc. for work relationships.
Add track metadata plugin priority processing

All track metadata processors are equal but some are more equal than
others.

This commit allows a track metadata plugin to register with high
priority, and to run before plugins which are not high priority. This is
needed for the Standardize Performers plugin.
Add Standardise Performers plugin
Add NEWS