Add docs on how to get count of all rows in a dataset

[alaurenz]

Multiple people asked about this at Hack for LA and also in other contexts.

Might be appropriate to add on this page: http://dev.socrata.com/docs/functions/count.html

[marks]

@alaurenz the first example at http://dev.socrata.com/docs/functions/count.html seems to do this. Are you suggesting we have a count(*) example too?

[chrismetcalf]

I've been thinking of building in a way to highlight better these inline examples, almost how you'd see in a technical how to book. It's better to have them in context like that than on their own pages, but it'd be better to make them more prominent and maybe give them an "index".

[marks]

@chrismetcalf such as having examples like this on each dataset's foundry "page"?