Improve studies pages

Reworks the organization so that the links are for "Private and Shared" studies and then public studies.  The private studies (i.e., the studies that a user "owns") and the studies that are shared with the user are displayed as two separate tables on the Private and Shared page.

Also, adds a waiting page, which can be written to the response while other logic goes on behind the scenes (so that the user at least sees that the server is working).  I thought this was necessary because the private and public studies pages can take a while (~3 seconds) to load.