Add option to Docker provisioner to build local images
Remove defunct @build_options reference
[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}" }
```
Ansible Docs: Display multiline examples in block
Add unit tests for Registry#keys.
providers/virtualbox: allow and prefer static guest IPs for NFS

Since vbox guest properties are proving to be less reliable than we had
hoped, bring back the static config parsing mechanism for finding a
guest IP to hand to NFS. If we find a static IP (or set of IPs) we'll
use that instead of trying to probe guest properties.

This retains NFS support for DHCP interfaces while regaining the
reliability that we previously had when static IPs were required.
core: re-arrange some code to make things easier to read later
core: correct some doc comments
core: box add fails early if box already exists [GH-2621]
core: warn if no provider is specified that we can't check for it
core: undo last for now
providers/virtualbox: export after checking if package exists [GH-2380]
provisioners/chef-solo: delete data bag secret [GH-2712]
Merge pull request #2674 from phinze/static-nfs-guest-ips

core: problems with using VirtualBox guest properties for reading NFS Guest IP
Update CHANGELOG
v1.4.2
website/www: 1.4.2
up version for dev
Add funtoo guest support. Based heavily on https://github.com/mitchellh/vagrant/pull/1840
:fireworks: New year! :fireworks: