Add logging for when cookies are rejected

"cookie-rejected" gets emitted whenever a domain doesn't have permission to
set a cookie.
Only show green requests if they have trackers

Previously, 3rd party requests would show up as green in the panel if
they were on the preloaded whitelist or if were user-whitelisted,
regardless of whether they actually contained trackers. This changes the
behavior such that the panel only shows green requests when they contain
trackers.
Refactor and emit noaction on policy-whitelisted domains
Start accounting set-cookie when 3rd party cookies are disabled
Explicitly allow a cookie if user sets to green

This overrides the default cookie behavior.
Delete all cookies on shutdown if user chooses to

Partial fix for #85, not tested yet
Use object keys instead of sets in changedCookies

Sets is not fully supported in FF <24 and threw some inexplicable errors
in FF29.
Check cookieLifetimePref on startup
Merge branch 'master' into fix/issue-64

Conflicts:
	lib/contentPolicy.js
Only show the cookie warning in truly weird situations
Make UI consistent with users' default cookie settings

If user is blocking all cookies or (some) 3rd party cookies by default,
the UI should show these trackers as yellow, not green, before the
heuristic has blocked them.
Add comments, refactor cookie clearing
Merge pull request #90 from EFForg/fix/issue-64

Fixes #64, #85