iot-lab: fixed timer conf
example: cleaning up and using shell for OpenWSN example
uart: implement IRQ based UART rx for stm32f1
at86rf231: introduce variable to keep internal driver state

The at86rf231 radio transceiver provides one IRQ (TRX_END) signaling
end of transmission or reception but no way to distinguish between
these.

Conflicts:

	drivers/at86rf231/at86rf231.c
core: a few more debug information
at86rf231: switch back to rx after rx
openwsn: use thread_sleep instead of yield