Add documentation for using pycharm to develop and debug

I have been using the pyCharm IDE for awhile now and I find it to be quite nice when it comes to developing and debugging horizon (and other openstack) code. Without existing documentation, I had to do a bit of trial and error when I was getting things set up and I have had other people ask questions in IRC about what I did to make it work.
I'd like to add some documentation for the Liberty cycle. Hopefully, it will lower the barrier to entry for other developers that would like to use pyCharm on Horizon.