since it is now possible to have different svg/framesvg with
different themes, s_sharedFrames must be indexed by theme first
what it's really the identifying thing is ThemePrivate, so it's indexed by that
this fixes a crash that occurs the second thime the theme gets changed
BUG:335472
All cpp code moves into the src/ subdirectory, as the Frameworks policy
suggests.
Directory structure should now be in line with other, future frameworks.