Make Sandcastle autocomplete work without combine step.

Sandcastle had an uneeded dependancy on `Build/CesiumUnminified/Cesium.js`
(generated during the combine step) since the `Source/Cesium.js` file could
provide the same functionality (and is created during the build step).

This means that for a fully functionaly sandcastle you only need to run
`build` and `generateDocumentation` which is way faster than
`combine and generateDocumentation`.
Fix punctuation in comment.
Merge pull request #2164 from AnalyticalGraphicsInc/sandcastle-tweak

Make Sandcastle autocomplete work without combine step.