Fix building of static media for extensions.
The static media building support for extensions depended on a

settings_local.py file somewhere in the path, which we had due to

running setup.py develop on our dev environments, but users won't on any

site installs.
We now package a nearly blank settings_local.py file and use that for

the static media building.

Successfully built a package without having a settings_local.py in my main path.