customize transit export plugin based on system config

based on system-config it should be possible to decide, wether

• the value of the manually setable status field and / or
• the terms found in the source segment
  should be added to the "Notizfeld" of the target segment in transit

If the source terms are added, the corresponding target terms are added to the Notizfeld of the target segment, too. But: The corresponding target terms are added from LEK_terms in the DB - independently of their appearance in the target segment.

Another option should decide, wether the adding of found terms in source and target is done only for the writeable segments in translate5 or for all segments.

A third option should decide, if for locked segments always a certain status is written to the Notizfeld of the target segment. The system config should also determine, which status should be set (for the current project this should be set to ""keine Änderung nötig"".

For every addition to the "Notizfeld" the date when it is added should be added, too.

Later this should not only be done based on system config, but also on task config (through GUI and API)