Expanding the documentation

The main readme only says "planetary surface data input/output library ". It is not clear at all what that actually means, where are the inputs coming from, what to do with its outputs, how it plays with other ISIS tools, and what this program is good for.

It would be nice to have an example, say using a few satellite images (if that is what it is for), create some of those points, read them or write them with this tool, show how to import them in jigsaw (or is it the other way). Also if it has anything to do with MOLA.

Start with the main README and map the questions it leaves unanswered: input sources, outputs, relationships with other ISIS tools, and the program's purpose. Review the requested satellite-image example, point creation and reading or writing, jigsaw import direction, and any MOLA connection; done means the README explains these workflows clearly with a concrete example.

Written by the indexing model from the issue text.