Final step for Release 1.2.
Removed unused imports.
Updated unit tests
Several changes: - Backends need no longer be listed in backends/__init__.py - New spoolerctl command "rmbackend" to remove backends that crashed or otherwise disappeared - Introduced root user; some commands now require root privileges
Added messages to all test cases. These messages will be shown if a test case fails.
Added some more test cases.
Initial check-in. A set of unit tests; not yet complete. Use runalltests.py to run all unit tests at once.