Populate example list exclusively via javascript.

This removes the duplicate logic for populating examples on first load.
Add demo3-specific examples
Allow Examples page to return different subsets of results
Create a demo3 page with different example queries
Merge from origin/master
Update sigma-clipping example
Add page rank example
Fix capatialization
geographic center of mass
standerdize capitialization
Merge pull request #114 from uwescience/language_demo

Allow for custom example pages