Change UIPs description in Readme 

UIP has just had a change in direction that it is headed. See here: https://gitter.im/NIT-dgp/General?at=5a2142663a80a84b5ba3d660 
Accordingly a change in the Readme has to be made, with changes with occurrences like `UIP is a desktop wallpaper changer` to `UIP is a desktop customizer`