Added "Windows Phone 8.1" as target of the portable class library "PropertyTools"
Added "Windows Phone 8.1" as target of the portable class library "PropertyTools"

objorke/PropertyTools,punker76/PropertyTools,jogibear9988/PropertyTools,LavishSoftware/PropertyTools,johnsonlu/PropertyTools,jogibear9988/PropertyTools,ZHZG/PropertyTools,Mitch-Connor/PropertyTools,ZHZG/PropertyTools