Merge branch 'jk/notes-merge-config'

Merge branch 'jk/notes-merge-config'

"git notes merge" can be told with "--strategy=<how>" option how to
automatically handle conflicts; this can now be configured by
setting notes.mergeStrategy configuration variable.

* jk/notes-merge-config:
  notes: teach git-notes about notes.<name>.mergeStrategy option
  notes: add notes.mergeStrategy option to select default strategy
  notes: add tests for --commit/--abort/--strategy exclusivity
  notes: extract parse_notes_merge_strategy to notes-utils
  notes: extract enum notes_merge_strategy to notes-utils.h
  notes: document cat_sort_uniq rewriteMode