Fix install script.

The working directory is now set correctly.
Make the logging format accessible through constants.

Before, they were hardcoded.
Fix main executable.
Update dependencies in setup.py.
Update tests.
Simplify sleep algorithm.
Add methods to share data with other backup folders.
Fix construction of the rsync logfile path.
Tidy up core modules.
Add first draft of a man page.
Add some sphinx documentation.