Fill out colorbar definitions for all common variables

[jfrost-mo]

What problem does your feature request solve?

When a variable does not have a colourbar entry plots of it will scale differently and thus be hard to compare. To prevent this we have our style file, however it doesn't contain all the common variables.

Describe the solution you'd like

Add colorbar entries for all common variables, with sensible colour maps, and reasonable ranges for a "default" look.

This will require consulting with scientists to get colour map preferences and expected variable ranges.

Describe alternatives you've considered

While we could keep adding on an ad hoc basis this will talk a long time to achieve significant coverage, and people might not bother.