string.xml: specify description for Open Loop setting
string.xml: specify description for Open Loop setting

Adding "Open" to description of 'Minimum request change' in open loop mode and adding " in %" to value,

so that people immediatly know for what it's for
Heiner1/AndroidAPS,Heiner1/AndroidAPS,jotomo/AndroidAPS,MilosKozak/AndroidAPS,jotomo/AndroidAPS,Heiner1/AndroidAPS,PoweRGbg/AndroidAPS,winni67/AndroidAPS,MilosKozak/AndroidAPS,Heiner1/AndroidAPS,jotomo/AndroidAPS,PoweRGbg/AndroidAPS,PoweRGbg/AndroidAPS,winni67/AndroidAPS,MilosKozak/AndroidAPS