Lack of error checks on profiles

DefaultProfileManager performs no error checks on the profile IDs So If I specify bogus profile IDs from plugins (like mvn -P no-such-profile), Maven doesn't complain, and it just runs as if nothing was specified. This is very error prone.

Also, I've seen some documentation that says deactivating a profile is "-P !profile". As far as I can tell from the code, this is wrong, but because of the lack of error check, such usage just gets ignored, and the user is left confused as to why the profile isn't deactivated.