Fix typos in theme config & update it
Device modules now can specify default theme

This is currently used mainly to set a Silica compatible theme
when running on the Jolla device. But the traditional
"default" and "night" themes can still be used. :)
Add initial Silica theme and use it by default on the Jolla
Fix pinch-zoom

Looks like MouseArea needs to be a child of
PinchArea for both pinch & drag to work.