Further work

[almarklein]

• Flexx should have a function to get access to the handlers to add.
• How to deal with tokens?
• CI, even if its just flake8.
• Should this repo be in the JupyterLab org? (here is probably fine)
• Should this package be renamed? ("flexxlab" seems easy enough to remember)
• Let plugins provide a service (that other plugins can hook into).
• Idea: a way for the user to interactively create UI's from within JLab. Would have to see how that works out with server / kernel communication.