Allow [mv] on first line, or sign should turn red if [mv] is on first line

[uglycoyote]

It took me literally hours of fiddling with this plugin before I figured out that the signs were not working because I was putting [mv] on the first line. I realize now that the instructions did say to do this, but it would have helped if there was more feedback. (Since the sign was not going red, I assumed that the plugin was just not installed correctly or perhaps not comptable with the server I was running.)

[zax71]

I think this might be better as a message to the player as turning red could be annoying if someone actually wants [mv] on the first line of a sign