Fix some errors in pingpair examples
Changed SPI_CLOCK_DIV16 to SPI_CLOCK_DIV4
Added nRF24_Serial_Chat to the examples

This example is an interactive chat using the nRF radio, input from
Serial Monitor, output on the other end on either Serial or 16x2 LCD,
sketch works on both sides a I swapped the Tx/Rx address before
radio.write
upd for self use