Changes in Interrupt core + example modifications

1) Attach interrupt now returns the interrupt ID - usefull to know in
interrupt callback function
2) When detachInterrupt can't detach interrupt instead of raising an
exeption it will return False
3) Minor changes in callback error handling
4) Added RotaryEncoder class
5) SH1x things on error now raise an exception
UPER SPI bugfix

Added a cast to int for  read_from_slave parameter and fixed a possible
Null error.