Add support for the modmore.com Redactor editor

Thanks for the pointers on adding support Bruno. This patch adds the necessary files to MIGX for Redactor. If you need anything else let me know.

(If you don't yet have Redactor set up, shoot me an email support@modmore.com with your modmore.com username and I'll set you up with a free license to test/improve this integration if necessary.)

EDIT: Forgot to add, this patch depends on the currently unreleased Redactor 1.2 which will be out soon.)