DOC: Make the getting started section a bit more readable to newcomers

[jonas8217]

The first section in gettings started uses the abbriviation CRS, it would be nice if the abbriviation was written out.
I think it would make it more readable for the unengaged (ppl like me).

So instead of:
"Using CRS"
somthing like:
"Using Coordiante Reference Systems (CRS)"

[djhoese]

Good points @jonas8217. Perhaps it could be better if the first paragraph or first section better explained what a CRS (the concept) is and how a CRS (the object) contains that information. Then the "Using CRS" section would be after and could be called "Using the CRS class".

Similarly, some of the docs could be restructured similar to the system described here where there could be a "Concepts" section of the documentation explaining CRSes, coordinates, transformations, datums, etc. However, these sections and these concepts would probably be better in the upstream PROJ C/C++ library documentation if they don't already exist.

Alternatively, a glossary of terms where "CRS" is defined and can then be linked to in the first sentence of the "Using the CRS class" section. Sphinx makes it easy to define a glossary of terms and link to the terms.

[snowman2]

Contributions welcome!