core-6020 prompt DE tour for new users.
core-6029 add support for searching items with tags
core-6029 add units for tagged item search
Merge branch 'dev' of github.com:iPlantCollaborativeOpenSource/DiscoveryEnvironment into dev
CORE-5960 Initial update of apps/categories endpionts
CORE-5960: Rename App/AnalysisGroup to AppCategory