Removed deprecated examples
API update

1) Added abstract core interfaces for GPIO, PWM, SPI, I2C, ADC. They
describe what functions should an implementing class must have. This way
we can unify many different boards.
2) UPER1 classes now implement core classes
3) Modules are not initialized by user anymore. Instead they are
retrieved by calling appropriate producer function (board.GPIO,
board.SPI, etc.)
4) Merged Interrupt into GPIO class
5) Changes to method and constant names, so that they would be a bit
more like in RaspberryPi and BeagleBoneBlack API.
6) Changed things and examples code, so that it would work with the new
API.
7) Code style fixes.