Added get_indexed_objects method to Page
Make search signal handlers use get_indexed_objects
Search: Added new deduplication method Fixes #710
Search fields can be overridden again. Fixes #709
Added system check for ForeignKey cascade

Pages can be linked to other Pages, Images, etc through ForeignKeys. If
the object being referenced by a page gets deleted, the page itself will
be deleted as well. Also, the page will not be cleanly removed from the
tree (leaving orphans, out of date num_child, etc). It is very common to
accidentally forget to set the on_delete action to models.SET_NULL.

This pull request checks all ForeignKey fields on pages and makes sure
that they are not set to cascade. If they are set to cascade, the
developer will be warned of their mistake.

This only works for Django 1.7 users as it uses the system checks
framework.
Fixed login form to reference USERNAME_FIELD

Was hardcoded to say 'username' when USERNAME_FIELD may be 'email' etc.
Updated LoginForm to dynamically set placeholder text

Placeholder text is now determined from the verbose name of AUTH_USER_MODEL's USERNAME_FIELD
Merge branch 'master' into custom-user-model-fixes
Use specific page class in all admin actions. Fixes #737
Merge branch 'master' into custom-user-model-fixes

Conflicts:
	wagtail/wagtailadmin/forms.py
Clear wagtail_site_root_paths on Site delete

Fixes #706
Merge branch 'master' into custom-user-model-fixes
Template: Deleted readme

Not needed
Merge pull request #754 from kaedroho/template-delete-readme

Template: Deleted readme
Merge branch 'foreign-key-system-check' of https://github.com/kaedroho/wagtail into kaedroho-foreign-key-system-check
Release note for #718
Merge branch 'kaedroho-foreign-key-system-check'
Merge branch 'clear-site-root-paths-on-delete' of https://github.com/kaedroho/wagtail into kaedroho-clear-site-root-paths-on-delete
fix inaccurate comments and duplicate definition of test_cache_clears_when_site_deleted
release note for #719