Should There Be a Forced Sync Message?

[eik-dahms]

When syncing an ARC the user could give a sync message but doesn't have to. As already noted in #198, in my opinion, sync messages should be useful and describe what happend to the ARC since it was last synced.

I would remove the optionality for the message complete. Meaning the user has two write something. This still leaves the posibility of having something like "Update" as commit message instead of something useful. One could try to have the user to write at least two words (with check for space or something). But I guess this is also related to user education. Maybe it would be useful to have a "good sync message practice" entry in the arcCommander documentation.