client log

As per @pblain request, the following requests will be logged with the following format:
 * Faceted search - `Searching collections: {"facets": [ ARRAY_OF_SQUASHED_FACETS ]}`
   * Squashed facets means that `[ "facet1/facet2", "facet1", "facet3", "facet3/facet4" ]` becomes `[ "facet1/facet2", "facet3/facet4" ]`
   * Squashed facets should make the log look cleaner
 * Collection selection - `Selected collection: {"title": "collection_title"}`
 * Filtering - `Filtering collection: {"title": "collection_title", "filters": [ ARRAY_OF_CQL_FILTERS ]}`

Then we probably want to include it in the rest of the requests as well (download too). Do we?