Fix typo in RFM_Struct_node

*radio.GetDataLen();  should be  radio.GetDataLen();
Updated example sketches to match lib changes

Changed variable access to accessor functions.
Changed wait for ACK from while{} to do{}while so that ACKReceived
always gets called at least once.
Merge pull request #2 from uChip/master

Updated RFM12B example sketches to use accessor functions