[#6701] Added access handler submitted by Rui Ferreira

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6701] Refactored permission handling

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6701] Refactored auth check

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6701] Changed ApacheAccessHandler.py to use Allura auth via requests

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#3815] Render return_to field on login form
[#6701] Improve reliability of auth check

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6701] Added support for virtualenv to ApacheAccessHandler

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6701] Return 401 Unauthorized instead of 403 Forbidden when anonymous access is denied to force client to prompt for auth

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6701] Don't send usernames and passwords in the URI (ends up in logs)

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6701] Must call get_basic_auth_pw before req.user

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>