Feedback from @homsrego
The images was too often updated during the scan. It was obvious is case of a display expecting a lot of data processing like histograming. The result was a processing on a GUI side much longer than the scan duration. This was not expected by the current design of Flint.
This MR fixes several issues in order to fix the problem.
- frame id was not taken into account (to filter already up-to-date image)
- image and spectum events was duplicated (triggered by there specific events + the one from the group of scalars)
Plus few other typo and fixes.