49 heatmap mitigator name v2

[craig-parylo]

Closes #49

Changes:

• Adds checkbox-controlled mitigator name / code in the heatmap plot
• Displays values with percentage formatting in the geom_tiles()
• Lots of logic to optimise x- and y- axes (see below)

x-axis optimisation:

• Mitigator names are string-wrapped at approx. half the maximum string length - as recommended in issue Show the mitigator name in heatmaps #49 to reduce increase space for the geom_tiles()
• Legend moved to bottom of plot to increase available horizontal space
• Scheme names (x-axes) have conditional displays - fewer than 6 schemes and the names are displayed horizontally with string wrap at 20 characters | between 6 and 11 names and they are displayed at 45 degrees with no wrap | 12 or more scheme names and they are rotated at 90 degrees to fit more on the screen
  

y-axis optimisation:

• vertical scrolling enabled by setting plot height to prevent ggplot from resizing to fit available space. (fits issue Consider scrollability in cards #51 )
• plot height is determined on a pro-rata height for each mitigator displayed plus a base height defined by how much the scheme names are rotated
• dynamic plot height enabled by reactiveValues object and additional observers to monitor state of selections

[matt-dray]

Great job, thank you for this! These are well thought-out features.

Your dynamic scheme-name labelling solution is a great compromise. I've added a small techdebt issue in #66 to worry about later.

I've also added #65 for us to think about consistency of presentation. I think percentage is the more intuitive choice, as you've used here.

One small thing before approval: can you add a title for the heatmap legend (perhaps my fault for not including one in the first place!)? '80% Prediction Interval' like in the pointrange plot, but we may need to be more descriptive when #10 is completed.

Happy to chat more about these.

[matt-dray]

Thanks!