Added copying license.
Revert "Added copying license."

This reverts commit cdacea630828d8adc5e9c23830c6e5b0a49de613.
Changed scraper interface design.
Updated design doc accordingly.
Removed scraper classes in prep for new scraper interface.
Added scraper interface.
Added SimpleScraper class.
Added SimpleScraper unit test.
Added ThrottledScraper and ThreadedScraper stubs.
Implemented ThrottledScraper.
Added ThrottledScraper unit test.
Various, minor fixes in unit test documentation.
Fixed minor typo.
Changed getter/setter access to public.
Minor bug fix in unit test.
Implemented ThreadedScraper.
Added ThreadedScraper unit test.