Fixed an issue where a cached page would be shown after logging in as a guest and then a user with caching enabled (patch by NaX and Junyor).  All tests now pass again.

Fixed an issue where users weren't logged out if they had first logged in as a guest and then as a user (patch by NaX and Junyor).  Added regression test and fixed some small code style problems along the way

Fixed an unreported issue where sites would not be accessible after upgrading if they were previously using the HTTP Auth with browser work-around setting

- Somewhat more consistent comment structure

Fixed a bug where users would get caught in an HTTP Auth loop on the logout page (and added a regression test).

- Renamed permission "access site" to more correct "access secured pages".  Users will need to re-enable it after upgrading
- Fixed HTTP Auth problems when caching was enabled (caused by using an uninitialized global variable) by doing a full bootstrap in securesite_init() instead of doing bootstraps separately in _securesite_filter_check() and _securesite_user_auth()
- Rewrote and separated a bunch of tests to make cache problems more evident
- Added some cache tests