Fixes the core to make seed papers be paper objects.

Modifies the implementation of uploadSeedPapers to use PQ.  Also moves
it into sessionManager.js, which is a more appropriate place for it.

The order in which JS libraries are loaded in the HTML was changed to
better reflect dependencies.
Better checks that optional callbacks are given to functions.
Moves code to initialize values of new paper objects to the constructor.
Rewrites the session code to use paper objects.
Rename PQ to P
Adds default values to new paper objects