Use Docker official IANA ports

Docker now has official IANA ports and these should be used instead
http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=docker
Fix issue with image directory creation task race
wip - fix deployment on GCE

update docker port to official IANA
Merge pull request #25 from brooklyncentral/fix/issue20

wip for issue #20
Merge pull request #21 from cpuguy83/patch-1

Use Docker official IANA ports
update readme
update README
Merge pull request #26 from brooklyncentral/updateREADME

updated to ensure it is self-contained for first time users
Automatically map PortAttributeSensorAndConfigKey attributes
Fail DockerHost setup if customisation exit code is not zero

Without the check the next step will fail instead, which is a bit
misleading when you're debugging.