Small refactor so that we first initiate the Navigation (ToolManager), before filling it with tools.

Added a nice utility API function, Navigation.addTools.
Update for Sphinx documentation
Moved default_tool initilisation to FigureManagerBase and cleaned.
Fix navigation
Temporary fix to backends
Merge pull request #1 from OceanWolf/navigation-toolbar-coexistence-event-framework

Navigation toolbar coexistence event framework