Timing diagram for WebJive

With a diagram like this a user would be able to quickly figure out if the expected changes are occurring, what time lag would exist across different devices, if a state is ever reached, how long a device would remain in a state. This would be much better than reading log messages.

This diagram is more important for non-real time monitoring (because of the latency needed to draw the diagram).

At the moment the spectrum display widget does not support enum-typed attributes (like obsState and State for SKA devices).

• the dashboard designer can drag and configure such a widget in the dashboard canvas
• 1+ devices can be specified in the y-axis, in the order that the designer wishes
  • he/she can decide that the device attribute/state should be displayed in an ad-hoc section, or by default the display will be done in a shared section (section and swimlane are used as synonyms)
  • a shared swimlane can be used for attributes A1,A2, ... only if the set of values of the attributes is the same
  • in no way attributes A1, A2 are placed in the same swimlane if their sets of values differs
• when running the dashboard, the widget displays state changes of those devices using a piece-wise constant function of time
  • the order  on the y-axis in each swimlane can be that induced by the "natural" ordering of the range of the attribute/state (eg. the order of the enum provided by Tango)
  • the y-axis is split into 1+ sections, depending on what is specified in the widget and equality of the sets of attributes values 
• realtime rendering is not required (as the diagram will be mostly used for analysing the behavior in the past)
  • such as detecting if a state transition occurred at all
  • or if two devices make the same transition at the same time or with a certain delay
  • or which devices actually make a synchronous transition
• when running a dashboard, the widget allows the user to switch between a "time view" vs a "change event view"
• the "change event view" shows all "change events" (ie. timepoints where an attribute or state of a device actually changed) on the x-axis, equally spaced.

Code is merged on webjive master branch: https://gitlab.com/MaxIV/webjive
Docs are available at: https://webjive.readthedocs.io/en/latest/timeline.html
Tests are available at: https://ska-telescope.gitlab.io/-/webjive/-/jobs/1049176968/artifacts/build/coverage/src/dashboard/widgets/Timeline/index.html
Code is available both on SKAMPI mid and low