All applet plugin follow standard plugin convention: __call__ return applet class.
To add widget in mainwindow and fill menus, just call "graft(mainwindow)" method.
Improve PluginManager.instances, get_applets
Move oalab.plugins interfaces to core.plugin
Real oalab plugins like applets, paradigms, remain in oalab.plugins
First draft to create a GUI inspired by Blender 3D GUI
Add applet icons
Move all plugins linked to plantgl in plantlab
Blender ui become a module instead of simple script
Fix --debug-plugins command line
First draft to migrate OpenAleaLab MainWindow to SplittableUi
Improve and simplify PanedMenu
Add global menu
Fix minor bugs and improve PluginInstanceManger error messages
Add test to oalab/example/test_project