5.3.0-bem2 Docker CE and EE repository support

Adds support for Docker CE and EE repositories for Debian, Ubuntu, Fedora and CentOS.

5.3.0-bem2

Rebase to garethr-docker master.
Add functionality and tests for removing init.dk file on Docker::Run ensure => absent

v5.3.0-bem

Relax name sensitization. Allow underscores in sanitized names.