Add Category Shading (Series Colours)

[Daniel Marsh-Patrick]

Add dynamic mapping for data series and allow individual colour configuration.

[Daniel Marsh-Patrick]

As this one was a bit tricky, it's probably worth documenting some of the high-level changes:

• We had to swap the grouping around in capabilities.json as while it looked right, Power BI wasn't able to treat our category as a proper category (that we could bind objects to).
• This resulted in our values being grouped by the number of data entries rather than distinct categories, so we needed to employ some 'unpivoting' of the new values to match the view model.
• The rest was fairly straightforward once this complication had been figured out.
• Business logic as follows:
  • If no category supplied, we artificially create one to add values to, otherwise we just iterate as before
  • We have two colour options:
    • All Categories (fixed property) - if set, then use this for all categories
    • By Category (dynamic binding, triggered by a toggle in the property pane) - if set, don't apply the above one and apply as specified individually

[Daniel Marsh-Patrick]

#9: Modified the view model mapping so that we can manage the changes in capabilites.json in a sensible way. This requires some more expensive processing but will allow us to store dynamic properties for the right category. We've relaxed our rules slightly for valid view model processing so we'll need to fix this up later, but for now this resolves #9.

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