[#853] Fix license facets

The current default facets were using a 'license' field which is not present
in the Solr index. Changed it to 'license_id' and added some logic in
package_search to return a display name for them.
[#830] Dashboard filter fix
[#859] Fix default sort ordering

The default sort ordering for dataset searches is supposed to be
most-recently-modified first, but it's actually most-recently-created
first. This appears to have been a typo/accidental change in this
commit: bc496ff. Change it back to most-recently-modified.
[#808] Fix unicode template 500 error