Import markerID for personID
As !35 (closed) diverged way too far from the master, this is the follow-up MR after !34 (merged) has been merged.
Following changes will be included with this:
- created Button to "import markerID"
- import and process a text file containing personID and markerID
- synchronize the markerID with the data from input file
- allow this as CLI option
- read and write filename to pet-file
Closes #54 (closed)