Check for invalid characters when renaming printers
Currently when you rename a printer from the printer details page, it will not check for invalid characters, and it does not report failures, so users are unaware that the rename did not occur. Added checks for TAB, SPACE, #, and / per the CUPS specs. This partially addresses issue #1008 It looks like that issue has been outstanding for a long time pending ui changes, so attempted to keep the ui / flow as consistent as possible. Used error handling from nautilus/files for file renaming as a baseline.