Require result parameter for JulianDate functions

1. Does not require a parameter for `fromXXX` and `clone`. (because that seems to be the pattern we are going with)
2. Used scratch parameters in places where it was easy to add.
3. I didn't try to optimize the Timeline widget since it's getting rewritten anyway.
Update CHANGES.md
Add FeatureDetection.hardwareConcurrency

Chrome Canary recently added `navigator.hardwareConcurrency` which exposes the number of physical cores on the client.  This is a simple change to expose that value (or a default if not defined) on `FeatureDetection`.

I chose 3 as the fallback because according to Steam's hardware survey (http://store.steampowered.com/hwsurvey/) (2 cpus 47.26% 4 cpus 44.94%)

This will be handy when we do #1437 (probably post 1.0), but is useful immediately for `Primitive` creation.
Fix DynamicPathVisualizer handling of ReferenceProperty

`DynamicPathVisualizer` was relying on a hidden `_referenceFrame` property on position objects.  This is not the case with `ReferenceProperty`.  This changes it to use the public API.

Also, the subsampling code for paths was not unwrapping `ReferenceProperty` instances, causing it to fallback to generic sub-optimal sampling.  This addresses that as well and adds tests to verify it.
`@Type` -> `@type`
Merge pull request #1835 from AnalyticalGraphicsInc/dynamicPath-referenceProperty

Fix DynamicPathVisualizer handling of ReferenceProperty
Merge remote-tracking branch 'origin/master' into julianDate-require-result

Conflicts:
	Specs/DynamicScene/DynamicPathVisualizerSpec.js
Merge pull request #1834 from AnalyticalGraphicsInc/hardwareConcurrency

Add FeatureDetection.hardwareConcurrency
Fixed context uint test
Merge pull request #1828 from AnalyticalGraphicsInc/julianDate-require-result

Require result parameter for JulianDate functions
Another IE 11 test workaround.  The test passed when ran alone.
Fix texture test
Updated CHANGES.md
Fixed falsely reported active uniforms in IE 11 for geometries and models
Fix subtle model picking bug introduced in 895987af3603429f73af4a7a31a82930ca44150d and exposed in IE 11. If the shader program for the color command had uniforms optimized out that were not also optimized out in the pick command, the uniform map for the pick command did not contain the uniforms.
Remove old test
Fix billboard test in IE 11
Cleaned up some Runtime errors
Merge pull request #1843 from AnalyticalGraphicsInc/ie11-fixes

More IE 11 fixes