notes_user_guide.txt

Here are some notes on the User's Guide that are out of scope for
simple comments.

There's no mention of DAP4 - we should talk about it in the parts of
the guide that describe the protocol:

* About - include that it's about both versions
* Somewhere: explain why we used different requests instead of version
numbers. 
* section 2.2 could be generalized a bit so that is explains the two
types of responses as Data and Metadata.
* Section 3.1.2 - the specific response types only include DAP2;
expand to include DAP4 with an explanation of which goes with which
* Section 3.1.3
** the part about the external data representation should be expanded
to include both DAP2 and DAP4
** Basetypes for DAP4
** Grid
** External Data Representation
* Section 4.4 - pretty massive
* Section 4.4.4 - significant new text

I think the client section could use some new text about why CF/COARDS
data and client tools that are aware of those conventions work so
well. Also, I think some discussion of ways to use Jupyter would round
out the client examples.