We have a singleton class ThemeInterface, which means that it
is global and exists only once. It's members are static, i.e.
also global. A message from the department of redundancy department?
In any case, that makes no sense. Let's just make these members
local to the class.
I would even rip out the whole singleton thing, since the object
is not accessed anywhere outside from QML. Let's keep it for now.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
79bf243ec0