Call after hook even when before hook redirects

A redirect in a before hook shortcuts executing the route, but
an after hook should still have an opportunity to see the request
just as if the redirect had happened in a route handler.
Add 'on_reset_state' hook

This hook allows plugins to reset global state at the same time
as Dancer does.
Merge pull request #921 from PerlDancer/topic/improve-session-cookie-support

Improve session cookie support (and fast session support)