admin: Lots of fixes for running the admin panel in a WSGI server. - Use new source APIs in the dashboard to open WIP files. - Fixed broken/outdated code in some views. - Fixed cases when Flask is not running at the root URL by using the `SCRIPT_NAME` variable somewhat more properly.

*.pyc
*.egg-info
.cache
__pycache__
venv
tags
bower_components
node_modules
build/lib
util/messages/_cache
util/messages/_counter
dist
docs/_cache
docs/_counter
foodtruck/static
piecrust.egg-info
piecrust/__version__.py
.ropeproject