Added a comment to explain confusion over some information in the datasheet concerning the Radio Data Rate (see the RF_SETUP register in the Register map table, where it says about the RF_DR_HIGH bits: 'This bit is don't care if RF_DR_LOW is set.' I am not sure if they mean that the value for RF_DR_HIGH (presumably when they added the 250kbps data rate in the Plus model) overrides the RF_DR_LOW bit, of whether the RF_DR_LOW bit, when set, overrides the value in RF_DR_HIGH. Since the RF_DF_LOW value was introduced with the Plus model, I'm guessing that setting RF_DR_LOW takes precedence over the value set for RF_DR_HIGH.
Added following function definitions: Radio_Configure_Rx(), Radio_Set_Tx_Addr(), and Radio_Configure().
Added compatibility for the new, slower 250kbps data rate in the nRF24L01+ model.