Ability to add and override redactor settings.

I needed the ability to easily add redactor settings (ie, from http://imperavi.com/redactor/docs/settings) so I added a simple way to do that.

The basic workflow:
* create a js file in a public location with all your redactor settings in it
* set the path to the file within your cms.php file.
* flush cache and the new settings will be added to your redactor settings.

Any setting you add that is already existing in the richeditor.js will overwrite the richeditor.js setting.