FIX Infinite redirects on conflicting fullSite cookie domains

They were both set for .mydomain.com and m.mydomain.com,
which could lead to different values based on which domain,
ending up in the redirects infinitely ping-ponging between the two.
Regression from e0ba458b
FIX Set cookie in days rather than seconds

Regression caused by moving from setcookie() to Cookie::set()
API Moved themes into separate repo

Copying themes on dev/build is not really a good idea,
and for most purposes you'll want another theme anyway.
It also makes tests less fragile in terms of expectations.