Improve DynamicScene path visualization

Previously, we were only using data points explicitly specified in the CZML to draw paths.  This change makes the sampling algorithm take a maximum step size of 60 seconds so that if points are further apart, we step in-between them.  This allows us to generate certain types of data (such as satellites) with a greter step size in the CZML.  For example, I regenerated simple.czml and it is now 50% smaller with no visual differences.

While the path code is still not in its final form, this change provides a big benefit from a minor tweak.  The easiest way to test this is to use the new simple.czml in master and notice how jagged the orbits are, loading in this branch shows smooth orbits.
Merge pull request #503 from AnalyticalGraphicsInc/sampledPaths

Improve DynamicScene path visualization