Improve NCSS docs and upgrade guide

[lesserwhirls]

Call out changes to NCSS service elements in 5.x (i.e. GRID and POINT have different service elements). Addresses #544.

[tlvu]

Wow, so many places !

Should there be an example with both Grid and Point enabled simultaneously at the same time for mixed datasets? Are there any bad side-effect if both are enabled at the same time?

[lesserwhirls]

Yep, a lot of place for sure (and several places already had the correct info). A few years back we started to break out the what we called the TDS user guide into four pieces - a server admin guide, a server admin quick start guide, an end users guide, and a tds for developers guide. There is currently a ton of duplication, but I will keep the files in sync for the time being until we can get things cleanly separated.

At any rate, mixed Point and Grid FeatureType datasets (see these netCDF-Java docs for more info) are not supported in NCSS. NCSS still supports point requests against gridded data (e.g. extract time series data from a grid point), but that all falls under the /thredds/ncss/grid service for "gridded" data.