Merge pull request #2635 from bbonamin/master

Fixes networking private network URL
[vagrant] Update Registry with #keys method.

This helper method to return the keys for the registry will give capability to eliminate some code. Example:

```ruby
keys = [] 
@subcommands.each { |k,v| keys << k }
keys.sort.each { |k| o.seperator "#{k}" }
```

Versus:

```ruby
@subcommands.keys.sort.each { |k| o.seperator "#{k}" }
```
Rename docker_client and docker_installer

We can rename those classes and remove the docker_ prefix as they
already have a module namespace.
website/docs: phrasal verbs [GH-2644]
core: box removal of a V1 box works
Merge pull request #2641 from arthurnn/docker_rename

Rename docker_client and docker_installer
Update CHANGELOG
provisioners/chef: fix node/client deletion when node_name is not set [GH-2345]

V2 config uses `hostname` instead of `host_name`.
add docker for redhat
Merge pull request #2649 from tnaoto/plugin-provisioner-docker-redhat

Add plugin docker provisioner for redhat
provisioners/docker: Check if epel-release is installed on RedHat-ian guests before attempting installation [GH-2649]
provisioners/docker: Move DockerConfigureVagrantUser capability up to Linux guests [GH-2649]
provisioners/docker: Display warning in case a version get specified on the Vagrantfile and the guest is a RedHat-ian guest [GH-2649]
Update CHANGELOG
Update CHANGELOG
guests/debian: fix dhcp assigned default to work
core: execute SSH commands in context of login shell [GH-2636]
core: -t/-T work for vagrant ssh -c [GH-2618]
core: put shell quoting into its own util class, it is useful
core: SSHRun uses new ShellQuote util