Regex check every admit entry, slow but needed for backwards compatibility

Various small refactorings and cleanups were needed.
Added acceptance tests for admit/deny with regexes.

WARNING: the acceptance tests do not currently work (they erroneously
pass). Reason is that I spawn 2 cf-serverd processes on localhost
listening to different ports, but cf-agent sends everything to the first
one because of bug in connection caching. Submitted redmine #4646.
Merge pull request #1444 from jimis/access_regex

Access regex