Add PropTypes to orderer

Summary:
Went through and added propType declarations to all the components in
orderer.jsx.

Planning to make my way through the rest of the widgets (I already have
some others done) while waiting for code reviews, if there are no
objections.

Test Plan: * Verify orderer still works and does not give warnings about proptypes

Reviewers: alex

Reviewed By: alex

Subscribers: alpert

Differential Revision: http://phabricator.khanacademy.org/D7014