This commit converts the internal format of KoShape to not be pixel based anymore, but to
be based on postscript-points. This means that a 50pt wide box will now have the same
width on screen for everybody (1.76 cm).

* created a temporary lib called 'externals' to include stuff for building convenience.
moved kcommand to that library.
* Imported KoZoomHandler, for the *Test* application; flake does not depend on it!
* Created KoViewConverter which is a very simple interface representing a subset of
what KoZoomHandler can provide.
* Adjusted all paint methods to correctly use this KoViewConverter class.