Fixed #14386, #8960, #10235, #10909, #10608, #13845, #14377 - standardize...

Fixed #14386, #8960, #10235, #10909, #10608, #13845, #14377 - standardize Site/RequestSite usage in various places.

Many thanks to gabrielhurley for putting most of this together.  Also to
bmihelac, arthurk, qingfeng, hvendelbo, petr.pulc@s-cape.cz, Hraban for
reports and some initial patches.

The patch also contains some whitespace/PEP8 fixes.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@13980 bcc190cf-cafb-0310-a4f2-bffc1f526a37