When changing the search page or histogram resolution, do not force a
full page reload, but change the URL. That triggers an update of the
stores involved in the search.

Refs #2488

Prevent the submit of new searches, and change the URL instead. That
triggers an update on the stores involved in the search page.

Refs #2488

Delay fetching search parameters to create widgets until the last
moment, so we ensure the parameters used are the ones from the latest
search performed.

Instead replace URL and let search stores to fetch new data.

Refs #2488

After the last changes in the search reload behaviour, remove the
`sortField` and `sortOrder` options from `SearchResult`'s state and rely
on `SearchStore` to provide the right values.

Since we don't reload the search page now, we need a way of giving
feedback to the user when the search is being loaded. This commit
introduces a loading indicator in the bottom right corner of the screen
for such purpose.