Adding support for colored mails.

This is a minor improvement upon the mail feature that adds the ability for colored mails to be sent. It was a quick fix, and I think it's pretty self-explanatory. I will note that FormatUtil.stripFormat removes all formatting, and FormatUtil.replaceFormat replaces all formatting with §-style (Minecraft) color codes. If the user has permission to send colored mails, then the mail will be stored with §-style (Minecraft) color codes.