[ENH] OWParallelCoordinates: Plotly-based

[kernc]

Issue

Fixes #2310

Description of changes

Remove defunct parallel coordinates widget; add Plotly JS graphing library; use it for parallel coordinates widget.

Includes

• Code changes
• Tests
• Documentation

[codecov-io]

Codecov Report

Merging #2327 into master will increase coverage by 4.28%.
The diff coverage is 35.53%.

@@            Coverage Diff             @@
##           master    #2327      +/-   ##
==========================================
+ Coverage   76.06%   80.35%   +4.28%     
==========================================
  Files         338      327      -11     
  Lines       59675    56464    -3211     
==========================================
- Hits        45391    45370      -21     
+ Misses      14284    11094    -3190

[astaric]

I have played around with the widget. It behaves strangely.

• When I click on an attribute in the list, selection keeps changing as I move the mouse around (as if it did not register the mouse-up event).
• The color combo also sometimes selects an item that is different from the one I clicked.
• When I add a new Parallel Coordinates widget to the workflow, connect it to data and open it, it performs 1-2 resizes before the plot changes to correct size.
• I haven't found a way to remove the selection.
• If I click on Optimize Selected Dimension and the plot is displaying more than 9 variables, nothing happens.

I have stopped at this point :)

[astaric]

While I would really like to see this merged, It will not make it to the 3.7 release.

@BlazZupan, @janezd, could you take a look and comment on this new widget? If major changes are required, I would rather have it included in prototypes first and then promoted to the core when ready.

[kernc]

Was worth a try. 😄

[kernc]

For the time being, obsoleted by biolab/orange3-prototypes#99.