Add placeholder texts to connect dialog.

Some users still try to enter a password in that dialog.
Try to make it even more clear what belongs in which field
by adding placeholder texts to the QLineEdits.

Hopefully fixes #1442
Shows move message if you moved a user from another channel into another channel
Show messages for priority speaker status
Add -limits to help text and improve man page
Update man pages author to "the Mumble team" and bump dates.
Translation update

Updating 'mumble_en.ts'...
    Found 1590 source text(s) (16 new and 1574 already existing)