Fix #390: No longer depend on return value of add-row handler.
Update the release notes for v1.7
Move the extensions docs into their own file
Merge branch 'master' into next

* master:
  Fix #390: No longer depend on return value of add-row handler.
Add a TODO
FeinCMS v1.6.4
Merge branch 'master' into next

* master:
  FeinCMS v1.6.4

Conflicts:
	feincms/__init__.py