Remove Robolectric.shadowOf methods in favor of the generated RobolectricBase.shadowOf.

Change Settings.NameValueTable subclasses to avoid annotation processor warnings.
Move ShadowWrangler.shadowOf to Shadows class in robolectric-utils module.

shadowOf is now a static method with no dependencies.
Renamed Shadows to ShadowExtractor and renamed RobolectricBase to Shadows.
Merge pull request #1371 from robolectric/shadowOf-references

Use annotation processor generated classes in robolectric core.