Move debug toolbar URL patterns higher.

Otherwise they're caught by the section fallback handler.
Add basic front-end instance creation form.
Disable site-wide caching and enable realtime indexing.
swap css inclusion order, so that styles in app.scss override those in django-sayit’s speeches.scss
dark body background
replace Add Instance form with custom html; hide green subnav on Add Instance page
make Add Instance form work for Editing too
space below Add Instance form
new Log In page
new Sign Up page
restyle Add Instance page to match login/signup pages
minor fixes to login and signup pages
Log in as part of instance creation, not first.

If the instance form is filled in when not logged in, it will stash the
form in the session and redirect to log in/sign up. Once that is done,
redirect back to the action asked for.
styling for message bar
avoid ugly underline on brand header hover
Merge branch 'user-instance-add' of https://github.com/mysociety/sayit.mysociety.org into user-instance-add
improvements to login message bar
styling fixes for multiple yellow message bars, and weird overflow clipping bug on form buttons