Unauthorized HTTP Response + tests.

Review: https://reviews.apache.org/r/21324
Fix inline base64 functions.

Review: https://reviews.apache.org/r/21796
Added Owned::release().

Review: https://reviews.apache.org/r/21721
Added TemporaryDirectoryTest fixture to stout tests.

Review: https://reviews.apache.org/r/21590
Added JSON support to flags.

Review: https://reviews.apache.org/r/21565
Fixed pointer ownership bug in Authorizer.

Review: https://reviews.apache.org/r/21727
Fixed an incorrect configuration option.
Updated flags in the configuration documentation.
Integrate Authorizer into Master.

Review: https://reviews.apache.org/r/21723