backup.py: Add python script that is capable of incremental backups to local target and encrypted backup of selected folders to remote target.

Both, local and remote version, backup a selected set of sources.
- The local backup makes incremental backups to a local hard disk
  encrypted via dm-crypt.
- The remote backup transfers selected sources to an encfs on a
  local hard disk (also encrypted with dm-crypt, as it currently
  is the same hard disk as for local backup) and transfers this
  encrypted encfs to a remote location (e. g. Strato HiDrive).
Fix: Call _freeSpace of _localDevice member in local backup class.
Bump version to 0.0.10.
Also delete excluded files and directories where applicable.
Bump version to 0.0.11.
sudo umount ... works more reliable than fusermount -u ...
Fix some variable references left over from last refactoring.
Bump version.