LayoutLib: support for Path and BitmapShader using delegates.

Also created delegates for all missing shader, xfermode
and patheffect classes. Moved the logic of the xfermode,
and patheffects that was in Canvas_Delegate into the
xfermode/patheffect classes, and added support (in all
3 clases) for knowing if the shader/xfermode/patheffect
is actually supported or not. Make use of fidelityWarning
in LayoutLog if they are not.