Refactor flag parsing utilities in opts/

Signed-off-by: Solomon Hykes <solomon@docker.com>
Merge opts/ into mflag/ to simplify the interface

Signed-off-by: Solomon Hykes <solomon@docker.com>
Fix regression in pkg/mflag.IP.String

Signed-off-by: Solomon Hykes <solomon@docker.com>

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: SvenDowideit)
add non-global Var's for the extracted Opt types

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@docker.com> (github: SvenDowideit)
merges due to rebase

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@docker.com> (github: SvenDowideit)
Fix docker create

Signed-off-by: Tibor Vass <teabee89@gmail.com>