Improvements around Sirius 2.0 and Mac OS X

With this set of commits, I am able to use Arduino Designer with Sirius 2.0 (I did not change the builds files yet) on Mac OS X. 

A new preference has been added to allow to specify the serial port. 
The targeted Arduino SDK is now 1.0.6 (avrdude.conf is not at the same location, checks needed on windows and linux).