Initial implementation of support for hierarchical facets (bootstrap3 on...

...ly).

This is continuation from vufind-org/vufind#164. Bootstrap 3 required less css hacking so this is a bit cleaner (and no need for jsTree 3 upgrade here anymore).

These comments from the previous PR still apply:

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.