Add "join/leave beta" buttons on webUI

[jacob.salmela]

Update Pi-hole from the GUI

This has to have been asked before, and I just couldn't find it. I'd like the ability to update the Pi-hole software from the Web interface. In a perfect world, I could select an option box to automatically update the software on a schedule or whenever the Pi-hole Version, Web Interface Version, or FTL Version gets updated by the developers.