Widget cleanup

1. The first parameter to each widget is now uniformly named and documented.  It can either be an element or string.
2. Each widget exposes a public `container` property, which is the element that was passed into the constructor.
3. `cesium-darker` is now the default theme, deleted `darker.css` files and replaced them with `lighter.css`  For each of use, there is now a `lighter.css` in the Widgets directory which just includes all other `lighter.css` files.

I plan on continuing widget cleanup, but decided it was better to make small, incremental pull requests rather than shoving everything together.
Merge branch 'master' into widgetCleanup
New Cesium packaging via makZipFile changes

1. The original zip file is still created, but now known as Cesium-amd-<version>.zip
2. A second zip file is also created, Cesium-<version>.zip.  This new zip contains only the minified Cesium, Assets, Documentation, and a new skeleton.
3. The new skeleton doesn't require a build process and simply creates the 3 main widgets on an empty globe (though we can change this).
Changes after review.
Merge branch 'master' into widgetCleanup
Update CHANGES
Comment tweak.
Doc tweak
Maximum bike-shedding.
Change TimelineDemo to reflect proper theme names.
Merge pull request #580 from AnalyticalGraphicsInc/widgetCleanup

Widget cleanup
Merge branch 'master' into packaging
Forgot to rename old zip file.
Fix warnings in newer JSHint, and improve variable names.
Merge pull request #585 from AnalyticalGraphicsInc/fixWarnings

Fix warnings in newer JSHint, and improve variable names.
Move skeleton.html build logic into `combine` target.
Simplify skeleton and rename it to HelloWorld.
Merge remote-tracking branch 'origin/master' into packaging
Fixes from my last commit.
Simplify fileset.