UI improvements

[kiramclean]

• check resetting empty facets always works
• optimize the way the table stretches
• elide excess description

[Robsteranium]

It'd be nice to show "15 datasets" above the table (e.g. on the left). This could become "x of y datasets match".

We could extend this to observations with something like "X datasets covering Y observations" (or perhaps "X/Y datasets covering W/V observations" - although this might be a bit over the top).

[kiramclean]

Done on the branch for PR #37 (mostly in a083c88c238f854eecca86d36a8d63314d1144c8 and 89fbf22c75386a56baf9376decd152dd4ea19879)

[Robsteranium]

The "clear filters" button link doesn't seem to work in this context:

• load /
• click "Product"
• untick "Sitc 4"
• click "Apply filter"
• click "Clear filters"

The facet controls disappear, the facet selections remain in the url, and the "clear filters" bit remains. I'd expect the facet controls to be reset to their default state, the url to be reset (e.g. to /) and the "clear filters" bit to disappear.

Not sure if this is a bug or data mismatch or something.

[Robsteranium]

I wonder if it'd be nice to have a visual similarity between the facet control and the column heading (to signal that these are related).