Introduced a new repository parameter named ticket_based_auth for use with perforce repositories.
When the parameter is set for a perforce repository it will used the ticket based authentication mechanism provided by perforce.
This security mechanism is required depending on the security level set for the perforce server.
The change also rewrites the PerforceTool get_file method to use the perforce API instead of calling the p4 command line utility.

I setup a local test Reviewboard and tried posting and viewing a review request against both a repository with ticket based authentication and one without.