Colons in command strings after the command name break import

I have had some issues with the MailhandlerCommandsDefault.class.php file in plugins/mailhandler/commands.

I have been using the mailhandler plugin extensively to import a lot of varied data into Drupal. I found that where a command value contained a colon (':') after the command name, importing would not function correctly. In addition, I noticed a problem where forward slashes in the value were interpreted as part of the regex pattern used to strip all commands from the message body.

I have made a patch which addresses both of these problems. Firstly, instead of exploding command lines at the colon character, I implemented a regular expression match which returns only that text preceding the first colon. You will see from my comments that the pattern is not very fussy as I couldn't find any validation being performed when commands are added.

The problem with forward slashes is fixed by using str_replace instead of preg_match.

This is the first patch I've ever made, I hope it's okay and is of some use. Please let me know if anything is wrong and whether these changes might be considered for commit.

Thanks for the great module!