Main submenu and explorer now disable eachother when clicked
tweaks
Add a test that checks for missing migrations

If there are any outstanding model changes that have no migrations, the
tests will fail. Migrations *must* be up-to-date before any code changes
are accepted, or before a new version is released. If they are not, it
causes havoc for all users.

The bulk of the test code is taken from the Django 1.7 `makemigrations`
command, and the South `schemamigration` command.
Fix wagtailimage migrations not using AUTH_USER_MODEL

This caused a false-positive when South checked for changes to models
and an AUTH_USER_MODEL was being used.
Move RegisterDecorator model into wagtail.tests.models

For some reason, registering it via a decorator as part of a function
call caused it to register itself in the wagtail.wagtailsnippets app,
which caused a false positive in the missing migrations check. Moving it
to the wagtail.tests.models file means it is registered in the correct
location.
Made missing migration error message more verbose
Add missing migration for wagtail.tests

It only appears in Python 3.x for some reason.
Fix unicode error caused by ascii format string
Fix variable name typo
[fix] mysql support #541
added thousands comma to dashboard stats without mandating l10n or installation of more apps
updated menu footer to use space better, be clearer
tweak to small avatars
tweak to small avatar spacing
Merge pull request #831 from davecranwell/nicer-menu-footer

Updated menu footer to use space better, be clearer in how it works.
Changelog and release note for #831
Merge pull request #822 from takeflight/bug/815-unicode-widget-error

Fix unicode error with admin widgets
Merge pull request #830 from davecranwell/thousands-comma-dashboard

Added thousands comma to dashboard stats without mandating l10n or installation of more apps
Changelog and release note for #830
Merge pull request #812 from davecranwell/fix/submenu-explorer-interaction

Fixed submenu and explorer interaction to address #678