#16 Persistent storage of data in svn-repository.

[Ivan Bogicevic]

All documentation data (including structures) must be stored in a xml-file within a subversion repository.
- Add an item "Storage Path" to the program settings where the user can give the path to the *.xml-file within a subversion repository
- Every "Save Changes" (in both content editing and structure editing mode) commits the new xml-file (without further checks)