Keep query results on one page

[stscijgbot-jwql]

Issue JWQL-204 was created on JIRA by Bryan Hilbert:

From the JWQL user survey:
When query results are returned, keep them all on one page if possible.

We previously split query results into multiple pages in order to speed up page loading for queries that return a lot of results. Maybe we can find a middle ground here. Keep the results on a single page unless the number of returned exposures is greater than some threshold?