Draft: Flint: Display reconstructed slice from sinogram

This MR display realtime reconstructed slice from sinogram.

• Allow to use real data to test (NXtomo used by the DAU)
• Create widget to display reconstructed slice
• Reach the data from the scan, not from the plot
• Allow to enable the tool from the scan info
• Maybe provide an OpenCL dialog to setup context
• Provide manual center position (or use nabu for auto detection)
• Reuse the opencl context instead of creating new once
• Polish
  • Fix refresh plot view
  • Update the action icon
  • Better dock integration
  • Save plot config

This can be used this way

flint()
import os
userscripts = os.path.join(os.getcwd(), "demo", "userscripts")
user_script_homedir(userscripts)
tomo = user_script_load("tomo.py", export_global=False)
nxtomo_filename = "/users/valls/nobackup/data/fullfield_bamboo/bamboo_dataset1.nx"
tomo.fullfield_from_nxtomo(nxtomo_filename)