CRM-20179 - Fix race condition on manage group page

[colemanw]

• CRM-20179: Upgrade jstree and other clientside performance fixes

[totten]

Nice:

• Works in Firefox and Chrome
• Works in hierarchies with 1, 2, or 3 levels
• The patch is scoped to a single screen, so it doesn't seem likely to have external side-effects.

I might wait for the test suite to pass -- but tbh, i don't think this affects anything with unit-test-coverage, so in a crunch we could merge anyway.

[totten]

Test failure in CRM_Dedupe_MergerTest::testGetCidRefs cannot be related to this change (templates/CRM/Group/Form/Search.tpl). Triaging separately, but I'll go ahead and merge.