Updated table and send/view functionality

1. DATETIME field for dueDate in PEER_REVIEW replaced by DATE field
2. SendPeerReviews.php now redirects to ListPeerReviews.php upon success
3. EditPeerReviews.php no longer prevents user from submitting review
criteria when one and only one filled criteria is present
4. Added pending and sent review lists and associated functions to
ListPeerReviews.php and PeerReviewFunctions.php