improve kmltools and documentation

[rjleveque]

Some new capabilities were introduced in v5.7.0 that aren't well described. There is a bit in this notebook but more should be put into the docs, e.g. on this page

Some new tools for making kmz files with multiple topo figures (e.g. water and land points separately) are not yet documented.

Making kml files to view fgmax results should also be described.

It may be possible to improve some aspects of animated kmz files for viewing time frames from a simulation.