Better viewer.zoomTo/flyTo for data sources

[mramato]

Right now, zooming to an entire data source uses the currently computed bounding sphere of all entities inside of the data source. For temporal data this can produce very poor results. We should probably add an optional DataSource.extent property that returns the overall extent of the data and then zoom/fly to that instead.

Forum discussion

[shunter]

I've also found that the default flyTo in CesiumViewer produces catastrophic results upon loading certain CZML. In this case, it's a CZML file containing data from http://apps.agi.com/SatelliteViewer/, so essentially 15k points in orbit.

Due to the size of the file (11MB) I can't upload here, but it's available on the AGI network for reference. Contact me for the file path.