Data source outline width

The bulk of this change adds geometry outline width support to the `DataSource` layer. This is exposed via a new `outlineWidth` property on `EllipseGraphics`, `EllipsoidGraphics`, `PolygonGraphics`, `RectangleGraphics`, and `WallGraphics`.  For non-time-dynamic data, `StaticOutlineGeometryBatch` now groups geometry by width before splitting them into translucent/opaque groups.  Time-dynamic data regenerates geometry every frame as it was already doing (but now includes outline width).

Also:
* Added `outlineWidth` support to CZML geometry packets.
* Added `stroke-width` support to the GeoJSON simple-style implementation.
* Fixed external Khronos links in documentation.
* Fixes some bad tests for the above graphics classes and also added missing variable declaration from their constructor functions (and of course add tests for the new functionality).
* Also added a private function `Context.putLineWidthInValidRange`, which clamps the value to line widths supported by the underlying WebGL implementation.

Should we add information somewhere regarding browsers only supporting a line width of 1 on Windows?  I'm sure it will continue to be a common question on the mailing list; more so now that we're exposing it at a higher level.
No problem, wasn't sure if Scene or Context was the more appropriate place.  I'll leave it private for now, we can always expose it later if we need to.