doc: getting help
doc: cleanup + consistency

Platform supported -> Platform Supported
samples: these are specific to bob, so only load the bbb host
rpi: led support

this adds support for controlling the green LED (the one next to the red
power LED)
allow lazy initialisation of the drivers

this allows brevity in the sample codes (and should not be misutilized
in real world applications)
samples: simpleblinker rpi example

does not cleanup up after itself, but is concise