Fetch search results until screen is filled

The WWW UI has been modified to fetch search results, in the same way as
when a user scrolls down, until either the screen is filled with search
results or we reached the end.

Part of #264
Fix in collapseClick and timing on all queries

Made sure that the smart_search queries performed when expanding a
prefix (the collapseClick method) has offset set to 0.

Modified the next page and collapse expansion methods to also measure
and print out the query time.

Fixes #264
Merge branch 'www_ui_fill'