Add new configuration for mounting devices.
Add support for multiple "=" per line.

Before, when multiple "=" were present, unpacking after split() failed
and an error was raised. Now, partition() is used instead of split(),
which splits at the first occurence of "=" and returns a tuple
containing the first part, the separator ("=") and the second part. By
unpacking this tuple and just ignoring the separator we have the exact
same functionality when only one "=" is present, but e.g.

    device="UUID=abc"

will be parsed as

    (device, "UUID=abc")

which is desired behaviour.
Add first working implementation of automounting.
Add keep keys in rbackupd.conf (again).
Fix wrong logfile format if not defined.

Beforehand, it was set to "None" (literally) if not set, now, the
parameter is just omitted in this case to use the default.
Implement intelligent handling of overlapping backups.

See doc/ideas/what-happens-when-backups-overlap.txt for further
information.

Generally, it adds an option to the configuration file to specify what
should happen when backups overlap. The implementation is not thoroughly
tested. Additionally, it really complicates __init__.py, so refractoring
might be indicated.
Refactoring.
Merge branch 'overlapping-backups'
Merge branch 'automounting'

Conflicts:
	src/__init__.py