Allow explicit specification of navigation extensions, deprecate the auto-discovery behavior
Implement a composition of Inheritance 2.0 and response header setting

Refs #553.
Fix an inconsistency in feincms_nav (more details in the release notes)
Fix page_is_active with page pretenders
Add a test for page_is_active
Add @unpack tests
We do not have to support _meta.module_name anymore
@monkeypatch_class was never used inside FeinCMS, remove it
Remove another helper which is obsolete now that the minimum required Django version is 1.6
Update the release notes for 1.11
Merge remote-tracking branch 'origin/mk/explicit-navext' into next

* origin/mk/explicit-navext:
  Allow explicit specification of navigation extensions, deprecate the auto-discovery behavior
Add release notes about explicit specification of navigation extensions