Hierarchical facets

This is an initial implementation of support for hierarchical facets (bootstrap only). Includes fixes to issues in hierarchy tree in bootstrap theme (encountered when upgrading jsTree).

This is a bit larger than I would have liked due to needing to upgrade jsTree. I also found a few bugs in the hierarchy tree code and tried to make it work properly when I converted it to the new jsTree. Minimal sample records for testing can be found at https://github.com/KDK-Alli/NDL-VuFind/wiki/Hierarchical-Facets-Sample-JSON

The UrlQueryHelper changes were done because getParamArray is so slow that it caused a severe slowdown and I couldn't come up with a better solution. Maybe another solution could be devised for an overall performance improvement.

Changes in Results.php should also improve performance when retrieving coordinates for map display.