Feature & Bugfix Release

Major changes:

• Added PID Tuner output
• Added average temperatures for more stable temperature display/handling
• Added "Max. Temp" setting (which is required for PID Tuner steps)
• Enlarged PID constant length from 3 to 4 int digits
• Fixed possibliy wrong PID derivate calculation as discussed here

First public release

There's still a lot to do, but it's already working quite well