Add new sensor type S_GPS and corresponing V_POSITION holding location

and altidude.

New Example showing how to send position data and extract atomic time
from GPS.

This PR also fixes a couple of compiler warnings:
WARNING: Category '' in library XXXXXX is not valid. Setting to
'Uncategorized'

libraries/UIPEthernet/library.properties

@@ -4,6 +4,7 @@ email=Norbert Truchsess <norbert.truchsess@t-online.de>
 sentence=Ethernet library for ENC28J60
 paragraph=implements the same API as stock Ethernet-lib. Just replace the include of Ethernet.h with UIPEthernet.h
 url=https://github.com/ntruchsess/arduino_uip
+category=Communication
 architectures=avr
 version=1.04
 dependencies=