Added preliminary i2c framework
Minor cleanup
some more xio polling support
I2C expander polling ready for testing.
Added wiring diagram
Fixed reset connection on schematic
Fixed the chip identification message and added some chip debug output.
Fixed wrong debug read address
Added more status info at startup.
Bumped up the verion number.
Fixed MCP23017 port B identification bug
Added decoupling capacitors to the expander
Fixed xio interrupt handling bug.