Rework providesprocessor to generate ModuleAdapters even when no Provides methods are present.

This averts needing to fall-back on the reflection back-end in the case of no provider methods.  Also adds some tests for stateful modules used in extension graphs, and fix some error text related to module instantiation.
Accept dagger.Module in the processor, and don't assert that this processor has completed all processing for dagger.Module.  Also fix some nits.
fix checkstyle violation.
Fix some exception text, add a better thrown error for inaccessible no-args constructors on modules, remove a redundant test, and rename a provides method.
Revert from throwing a friendlier error in a case that should never occur outside of an applet.
Merge pull request #168 from cgruber/supportstatefulrootmodules

Generate ModuleAdapters even when no Provides methods are present.