Change SPI phase to 1.

According to the data sheet the MRF24J40 should use SPI mode 0,0. Using
that mode it does not respond, with phase=1 it responds.

Changed the baudrate with it.
Added more register values.
Change from numeric to symbolic values for init.
Change delay values to 1 ms.
Use bytearrays for TX and RX.
Fix brackets of assert
Add function to get the channel.
Return RSSI and LQI for received packet as well
Whitespace and comment cleanup.
Comment test code.
Add commented debugging code.
Add test module for the MRF24J40.