Update Page.register_extension example in docs
Docs update - display full module path for extensions

Shorthands were deprecated in FeinCMS 1.6 and removed in FeinCMS 1.8
Merge pull request #517 from bmihelac/patch-9

Update Page.register_extension example in docs
Merge pull request #518 from bmihelac/patch-10

Docs update - display full module path for extensions
Merge pull request #519 from DrMeers/next

Update model cache clearing to be compatible with Django 1.7.
Prevent a crash in feincms_nav by returning early when page is None
Merge branch 'master' into next

* master:
  Docs update - display full module path for extensions
  Update Page.register_extension example in docs
Fix #522: django.contrib.markup has been deprecated

No strong preference for markdown, it's just that I remember the syntax :-)
More copy-pasting
prevent PageAdminForm from blowing up if passed instance=None