Allow site to be Turned Off/Closed.

[ryanhowdy]

During upgrading, it would be beneficial to turn off or close the site, preventing people from messing up the upgrade process and also preventing them from seeing any errors that may be visible during the process.

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'''SOLUTION'''

As part of this ticket, the login system has changed dramatically, some major changes are:

1. The login redirects have changed from meta-refresh to header(). this is faster and prevents the stupid "Already Logged in: Continue" messages from appearing.
2. when a user tries to access a page without logging in, they are now redirected automatically to the login page, and also redirected back to their originally desired page after a successful login.