This broke at some point, let's fix it again by moving to the drawing and
calling refresh() from there - no need for the DrawingPerspective to call into
the drawing here.
Drop the user-visible separation, make everything just Tuhi. Directory
structure remains largely separate (tuhi vs tuhigui) except for the po files
which are in the top-level directory because convention.
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>