[Fix] Adding support for colored mails. Update of #770.

Attempting to fix the compilation failure with my previous PR, #770.

#770 was 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 was 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.