Add dirutils

This is a slight modification of the dirutils
located in ep-engine. It use a different namespace
and:

 * does not return "." and ".." in the lists
 * Strips multiple \\

Change-Id: I84c4a9aaff16121c2d66127175a14bd0035aca46
Reviewed-on: http://review.couchbase.org/31417
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>