Adding shoutbox feature for user pages and user's dashboard

@cgruppioni @chukdisc

I also know that I'm using _path for many link_tos, but those are all placeholders until I actually use them. Also, wouldn't mind tips on what I should be doing with my divs, classes and ids + css.
I feel like this is a validation that the sender can't be the receiver? If it is it should be in the model