Hide features of old Serviio Version

[Aziz Rahman]

Its brilliant that you have made Settings that don't exist on an old server version hidden. Two other things that can be ommited is drop down of Online Source type. From 0.6.1 other source types were available

The other is Thumbnail URL, this can be hidden as this is a 0.6.1 feature

[Will Lunniss]

Fixed for now, if anyone finds more for 0.6, please re-open this one (so there is one, this feature shouldn't be shown issues for each server version)