Add packaging readme

Document the experimental workflow as it's a bit complicated.
Rewrite debian/rules to use dh

Results in a cleaner rules file and, as a side-effect, solves
the double building issue described in #744050.
Release 1.4.7-2
Fix typo in recent changelog entry
Imported Upstream version 1.6.0
Merge tag 'upstream/1.6.0'

Upstream version 1.6.0

# gpg: Signature made Thu 24 Apr 2014 05:35:14 PM EEST
# gpg:                using RSA key 0x11362600A747ECD9
# gpg: Good signature from "Christos Trochalakis <yatiohi@ideopolis.gr>"
# gpg:                 aka "Christos Trochalakis <yatiohi@gmail.com>"
New upstream release
Enable auth request http module everywhere
Remove already present openssl guard patch
Update README.Packaging now that 1.6 is stable
Release nginx 1.6.0-1