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
Merge remote-tracking branch 'origin/master' into julianDate-require-result

Conflicts:
	Specs/DynamicScene/DynamicPathVisualizerSpec.js
Merge pull request #1828 from AnalyticalGraphicsInc/julianDate-require-result

Require result parameter for JulianDate functions