blissscan-handler: Rework new data event

This MR is an important change on the way data events are retrieved from BLISS.

• Added channel_name, channel_progress to the callbacks
  • This can be used for MCAs and images to follow a specific channel (which could have a different progress)
  • Except for scalars (there is still a global one which is named 0d)
• Added channel_size to know what was received for the specific channel
• channel was internally renamed master (cause it's about the master channel)
  • I did not changed the key on the scans provider, but this could also be done
• Make sure there is no dup events
• Make sure unsaved scans from Lima are properly handled (sct/ct)

This is still compatible to BLISS 1.7