User Login Functionality

System now supports very basic user authentication.  Currently only
checks that any user was successfully logged in by matching a username
and password to the employee table. It does not currently check if a
user is an admin, etc. They also have basic real escape cleaning of
inputs as well as md5 password encryption.

A basic validation/redirect script is included but commented out in the
top of the calendarView.php. If uncommented any attempts to view
calendarView.php without logging in first gets redirected to the login
page. Log out also works.  The login is currently session based. The
p3_scheduler database is used.

I hope this doesn't break anything for anyone else.