#571: start of implementation for creating tab for each label.
implemented multiple labels per example, via CSV
#571: de-cluttered main tab cluster by putting labels in subtabs of Gallery
#571:  Added label meta data to a few examples
Merge remote-tracking branch 'agi/master' into sandcastleGalleryLabels
Gave search results it's own tab, which displays when the search is not blank (else, its hidden)
renamed label meta tag to 'cesium-sandcastle-labels'
clean-up
Merge pull request #635 from hpinkos/sandcastleGalleryLabels

Sandcastle gallery labels