Decouple docker and sorter

In order to move the sorting into utils I needed to decouple it from the
main docker packages. In order to achieve that I have created a private
interface.
Decouple sorting by removing use of "Port"

Port is a type definition equal to "string" except it is declared within
the docker package. In order to move sorter into utils I need to remove
the couplings.
Decouple Container for sorting

Decouple Container so the sorter doesn't need to understand the full
struct.