Auto-logout on index if already logged in

Added logic so that if the user is already logged in, but goes to index.psp,
it will log him or her out.  Thinking here is that the user should never
be confronted with a page asking him/her to login if they are already logged
in.
Fixes #202
Merge pull request #205 from adamrp/logout_from_index

Fixes #202, Logout from index