Add more control over font sizes

[xylar]

A default font size of 10 is added to the config file. This allows users to increase the font size of axis ticks, contour labels, colorbar ticks, etc. with relative ease. This can be useful for figures for publications.

A default cartopy font size of 12 is also added.

In the same sections where colorbar ranges, color maps, etc. are defined, the default and title fonts can optionally now be supplied. This applies to climatology maps, Hovmoller plots, transects, T-S diagrams and various time series.

[pep8speaks]

Hello @xylar! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2021-05-19 11:15:09 UTC

[xylar]

Testing

This was tested as part of an analysis test-suite run on Chrysalis:
https://web.lcrc.anl.gov/public/e3sm/diagnostic_output/ac.xylar/analysis_testing/chrysalis/add_new_transects_to_transport_time_series/

Here is an example from before:

And with this branch: