BUGS.md: update for gitlab, explain -v better

Freedesktop.org is our new forever-home. So track bugs there.
Also, -v should not be needed normally, really.

BUGS.md

 Bugs
 ====
 
-Bugs are tracked via at [github][github issues].
+Bugs are tracked at [fd.o's gitlab][gitlab issues].
 
 
 Debugging
 =========
 
 The daemon can be run in verbose mode with the command line option `-v`.
+This should normally not be necessary, except when debugging the DBus
+layer of boltd (the verbose output is indeed very verbose).
 To replace the currently running daemon and run a new instance of it
 in the forground, launch the daemon with `--replace`:
 
-    boltd -v --replace
+    boltd --replace
 
 
-[github issues]: https://github.com/gicmo/bolt/issues
+[gitlab issues]: https://gitlab.freedesktop.org/bolt/bolt/issues