Added PyplotViewer command support
Colormap limit setting in PyplotViewer
Only one coroutine creation per PyplotViewer instance
Colormap support in PyplotViewer added
PyplotViewer is pausable
Base pyplot updater class added
PyplotImageViewer added instead of PyplotViewer

PyplotViewer is now a base class for more viewer types.
Don't let the exception in redraw hook escape unnoticed
PyplotLineViewer for 1D data drawing added