Fix edits getting lost in Biblatex mode

This fixes a bug where edits made in a field on a
CompressedEntryEditorTab wouldn't get stored when the field editor lost
focus. At the same time, the classes CompressedEntryEditorTab and
EntryEditorTab are consolidated.
Merge branch 'master' into store-edit-fix

Conflicts:
	CHANGELOG
Merge pull request #18 from dahlheim/store-edit-fix

Fix edits getting lost in Biblatex mode