Refactor release editor validation code

 * Avoid creating a special case for editNote. Make the weird
   "errorsExistOtherThanAMissingEditNote" thing unnecessary.

 * Move validation messages out of text_strings.tt and into the actual
   templates where they're used.

 * Use the arrayTransforms library to speed up some aggregate
   validation routines.
MBS-7746: recording-work edits not generated
Only require an edit note when adding a release
Move computed properties that only access one observable into methods
needsMediums is a plain function
Remove elementToInsertBefore, add comment
CHOMP it all
Get rid of looong OR
s/tracksAreComplete/hasTrackInfo/g
Merge branch 'beta' into fast-series-ui
Fix MBS-7751
Merge remote-tracking branch 'bitmap/fast-series-ui' into beta

* bitmap/fast-series-ui:
  Fix MBS-7751
  s/tracksAreComplete/hasTrackInfo/g
  Get rid of looong OR
  CHOMP it all
  Remove elementToInsertBefore, add comment
  needsMediums is a plain function
  Move computed properties that only access one observable into methods
  Only require an edit note when adding a release
  MBS-7746: recording-work edits not generated
  Refactor release editor validation code