Decide maximum workset size (under 30s to load)

[jswatsch]

Once we decide, we can filter out any larger worksets from the interface.

[jswatsch]

@dkudeki and @jswatsch to experiment with different workset sizes

[jswatsch]

		STAGE	DEV
	number of items	summary widget	tag cloud widget
History of black writing	25	1.2s	2.2s
The black fantastic	82	3.5s	8.7s
Action and Adventure	139	29s	29s
19th c cookbooks	238	8.6s	54.7s
fewfwefew	408	41.2s	41.3s
size test medium-small	526	1m36s	3m
usa presidential papers	779	2m11s	3m

[dkudeki]

Set 400 volume limit for Public and Private worksets here: htrc/torchlite-frontend@1348cf4. Left Featured Worksets without limits so those don't mysteriously not show up, and so we could feature any interesting exemptions that we may find.