updated the POST /studies/new endpoint to create a new study in the db that's added to the current user's list of studies
changed the "+ New Study" RouterLink (which originally routed to a "new study mode" that didn't actually create a study in the db) to be an AppButton that hit the new endpoint, allowing for the deletion of all "new study mode" logic throughout the code (no longer have to account for the case of a study being in "new study mode")
changed the "edit" and "delete" buttons in the MyStudiesPage to be AppButtons as well for general consistency
changes
closes #71