Removed option to send private message if it would go to system. Closes

Closes #4292 

Clicking the message icon was showing user not found. Made it so message icon does not appear if message was generated by system.

![screen shot 2014-11-28 at 7 50 34 pm](https://cloud.githubusercontent.com/assets/2916945/5233224/45e981c8-7738-11e4-9278-fd0c4ac0246f.png)

I liked the ability to send messages to myself. It was useful for testing and potentially also useful for sending yourself notes. Maybe that's just me though. Does anyone else have any thoughts?