Only scan for relay node max 3 times per transmission attempt (to save battery)

Lower transmission speed to reach longer distances.

Remove RF24 to prepare gittree import.

libraries/RF24/tests/pingpair_blocking/test.ex

@@ -1,11 +0,0 @@
-#/usr/bin/expect
-
-set timeout 100
-spawn picocom -b 57600 /dev/ttyUSB0
-expect "+READY"
-send "1"
-expect "+OK"
-spawn picocom -b 57600 /dev/ttyUSB1
-expect "+READY"
-send "1"
-expect "+OK"