Closes #2289 (closed)
This MR aim to clean up custom plots in order to have an easier base code to maintain and a more consistent API between client and server.
- Clean up the way plot are stored in Flint
- Remove the dedicated API for custom plot (and use serialized functions)
- Use silx name for plots
- Clean up and enable back skipped tests
As result it is now allowed to hold in Flint any widget, while Flint can import its module. All the machinery is setup in BLISS side. This also provide move flexibility which could be used on a specific beamline to tune stuffs.