Intial commit, basic function.

Can send packet from one device to another, and receive it.
Add radio_event_handler to tx-app
Change segger serial and BOARD for tx.
Add flag byte to packet structure.
Change mode to Ble_1Mbit and set TIFS.
Try sending an ACK. Doesn't work properly.
Rename the radio event handler.
Working ACK-ing, but TX stays in RX.
Add radio states
Added gpio header.
Use gpio header for led toggling in apps.
Do pin toggling in radio for debugging.
Add led.h
Use led.h in apps
Remove gpio toggling from radio.c
Set radio state to volatile.
Enable RXADDRESS when sending, to receive ACK.
Add object files to gitignore.
Add packet_queue boilerplate.
Added test framework