New Request & New Deploy forms

This PR adds forms for adding a new request (on the requests table page) and for adding new deploys (on he request detail page).

Not finished, might encounter bugs, ready for review. Try it out @gchomatas @tpetr @timmfin 

TODO:

* Add custom executor artifact handling (currently the buttons do nothing).
* Add context-sensitive help messages on the right side depending on what's focused (might merge without this).

The aim is to have this before MesosCon so I'll be looking to finish and merge this late Weds / early Thurs.