initial commit of the custom raspberry_pi externals supporting read/write from digital pins, analog pins (using shield with a mcp3008 A/D converter), and netsend~/netreceive~ optimized for rpi (net objects being copies of work done in the core pd)

removed clicks from multitap using variable delay (now has different temporary artifacts that actually sound pretty cool).

added one more k12 object and updated pd.tk to reflect new items in the k12 menu (including new minimum size)

added new abstractions to the K12 module (still need to integrate it into pd-l2ork and add help files)

slowed down the rate of update to avoid choking down the GUI (bumped update of the wii speed from 1 to 25ms)

numerous fixes and improvements to abstractions and help files including reworked image drawing logic, improved metronome preset ordering and updated presets throughout the demo and help files, improved icons, clean-up and optimization, beter enveloping, and more.