Optimization/Improvements in pack search page

[ffont]

With the new UI, the search page got a new "display as packs" mode which is used to show list of packs (for example, the packs by a user) and allows to search for packs. However this page is a bit limited because:

• Packs are not indexed in Solr and we only group the results by pack, therefore we can't sort by pack properties
• Page loads are quite slow as the display_pack templatetag needs to show a lot of information and this takes time to compute (even if the number of queries has already been reduced a lot). Also display_pack does not use any type of caching I think.

I think that we should update the pack model so it stores more summary information that does not need to be computed every time the pack is retrieved (and which is updated on Pack.process) to make pack displays faster. Also I think it would make sense to add a new Solr core to index packs so we can directly search for packs and sort accordingly.

In addition, we observed there are some bugs with pack filters which should be revised:

• Some pack filters with character : in pack name do not work, also with character ". Maybe we should use the pack id to filter and only use the names for filter display purposes?