Revisit default "add_coastlines" script defaults

[kathys]

We may want to go over all of the defaults we are using for the variables available when using the add_coastlines.sh scripts. The white border lines can sometimes bleed into images that have alot of clouds, and the default resolutions may be a bit coarse.

[djhoese]

Talked with @graemely about this. We could revisit this, but we kind of both agreed that it will be hard to come up with a color for lines that works in all cases so maybe white is "good enough"?

For coarseness/resolution of the lines, I'm not sure we really mentioned it in our call and I don't really remember the original use case for why we needed to review these defaults.

@kathys What are your thoughts on this?

[kathys]

I do think we should go over this, but not for the Geo2Grid 1.2 release. I would push this to the next milestone (1.3).