fix issue with cropping and initial scroll region
utilise flags in update cycle for reposition and crop
reinstate some of old container functions

sub classing foo canvas...

Well now it'll return the correct numbers!

trying to find initial bump issues...

Better error handling too

contain  base  FooCanvasItems  to  draw features,  both  compound  and
non-compound.

CanvasItem is the first subclass, with an interface, which the rest of
the set inherit from.

Status:
Currently work in progress,  with some missing functionality in Glyph,
Text and Sequence Features