Make polyline Sandcastle examples follow surface

Two eamples that use Polylines were making them go well under the surface
of the earth.  I took the easy route and used generateCartesianArc,
but I guess in the long wrong we should consider adding a `followSurface`
option to `Polyline` as well.  Fixes #2109
Merge pull request #2266 from AnalyticalGraphicsInc/issue2109

Make polyline Sandcastle examples follow surface