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tree (leaving orphans, out of date num_child, etc).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
Added image filesize validation
Added max_filesize to all image uploader views
Fixed display of hidden fields on image add view

Same as #668 but for the old image add view
tweak to validator message. passing through max size vars
Refactored image validation into a custom field

This fixes issues with Django closing the image file before running
validators.
This may give a slight improvement in upload speed as the file doesn't
keep having to be reopened.
This unifies our image validation with Django's image validation so
error messages could be shared (not implemented yet though).
The code is more maintainable (the validators no longer need to be
called manually from the multiple image uploader for example)
Check image file size before the format

Checking the file format may take a long time if the uploaded file is
very big so it makes sense to check the file size first to prevent the
server being held up unneccessarily.
started adding pre-upload validation to images
started adding pre-upload validation to images
updates to how error message and accepted file type/size are mentioned by jquery upload plugin
less poluting method of variable scoping