All applet plugin now follow same API
All applet class can be instantiated with zero parameters
get_applet service is now based on PluginManager
Add a splitable widget that tries to mimic the Blender UI.
PEP8
Example to test blender ui
First draft to support OpenAleaLab applets
Load all applet instead of only oalab-tissue applets
Minor bug fix
Fix applet services