Update django-subdomain-instances to 0.7
Make sure an existing contenttype is renamed.

This migration was trying to change the (speeches, popolospeaker)
contenttype to be (speeches, speaker) which since 80e3f0b4325395951cf89,
probably already exists, causing an error.

Make sure any existing (speeches, speaker) contenttype is therefore
renamed first.
Merge branch 'new_subdomain_instances'