Trying to add a jump-capability to the playback service.

- AIDL got jump-method.
- MainActivity directs jump-calls to the playback-service.
- Worker now returns its point.
- XML-parsing refactored again: now an input stream is given to the pull
parser to parse.
Deleted obsolete files.
UI change: EditText is now a TextView.
Progress bar and required supporting code added. Jump buttons work as well.