Setup a nice py.test environment

Probably we should get rid of the global temp dir at some point and set
a per-test temp dir from within test cases needing one!
Prevent SMTP/ZODB connections during tests
Add coverage
Create app error
Adapt tests to the new database
Move location tests to py.test
Add aspects test
Remove old location test
Don't recurse into htdocs
Add tests for (non)bookable hours/periods