Copyright-holder and year information is extracted from git log.
git history begins in 2005. So (C) from 1998..2005 is lost. Also some
(C) assignment of commits where the committer didn't use --author.
This fixes an issue on MacOS/X to only show non-root volumes in
the file-open dialog. They're just as valid for save-as, export, video
files etc.
In case of a 2nd internal disk, it is also a valid choice as default
folder for new sessions.
* allow to take snapshots and save-as read-only session.
* change ambiguous "Save as" window title for "Snapshot & Switch"
* start save-as in configured session-dir
