Refactored database access: now supports multiple experiments with individual user tables and has separate master user table.
Updated admin gui to reflect database change.

Still to do:
-Build user login system
--Send users to new user page depending on experiment settings (anonymous means don't need account)
-Fix user invitations to use new experiment-dependent user tables
-Implement invitation expiration
-Fix admin gui so you can close tabs
-I think experiments need input validation