support synchronization with both puppet forge and a directory containing a pulp manifest and modules.
Add constant for PULP_MANIFEST.
Update docs.
Apply PR feedback.
specify unit key fields in criteria.
abort _run() when manifest cannot be fetched.
Add unit test for returned download reports.
progress report fixes.
Merge pull request #98 from pulp/jortel-US2486

Support both puppet forge and directory synchronization