Upgrade RequireJS to 2.1.2, Almond to 0.2.3.

Minor changes along the way: any comments containing "(c)" or "copyright" are now assumed to be copyright comments and preserved in the minified output, so I changed a few comments that were unintentionally treated that way.  The build now copies the RequireJS optimized worker layer files into the Dojo-built output folder when building CesiumViewer, to reduce the modules requested by RequireJS inside the web worker to 1.  The glslToJavaScript task no longer checks file modification times, so that changing the minification setting now actually has an effect without a clean.
Merge pull request #433 from AnalyticalGraphicsInc/upgrade_requirejs

Upgrade RequireJS to 2.1.2, Almond to 0.2.3.