Add default ports to PhutilURI
Summary: Add default ports to PhutilURI to allow the getPort() method to return the default port is no port number is explicitly provided.
Test Plan: Added test cases.
Reviewers: #blessed_reviewers, epriestley
Reviewed By: #blessed_reviewers, epriestley
Subscribers: Korvin, epriestley
Differential Revision: https://secure.phabricator.com/D11338