Fix doc link [GH-3978]

Fixes #3978
Add nixos guest capability: nfs_client_installed
Merge pull request #3983 from dougm/nixos-nfs-client

guest/nixos: nfs_client_installed capability
Update CHANGELOG.md
Fixed issue 3987

Reboot the Windows guest after renaming the computer so changes take affect immediately before attempting to provision the box.

- Changed rename from wmic to netdom since netdom seems to work correctly in Windows 2008R2 and newer OSs.
- Fixed Windows guest error translations, the wrong namespace was specified in the yaml file.
Updated the rsync freebsd plugin install process for FreeBSD 10
core: don't delete data dir if no data dir [GH-4017]
Merge pull request #4009 from calvinhp/fix/master/freebsd_rsync_install

guest/freebsd: update rsync install for FreeBSD 10
Update CHANGELOG
guests/freebsd: style
Merge pull request #4006 from mitchellh/fix-issue-3987

guests/windows: reboot after hostname change
Update CHANGELOG
fix escaping of powershell variable

As this is nested in a powershell variable $command, it must be escaped
otherwise it is evaluated when the variable is created, giving an error that
"The term 'True' is not recognized as the name of a cmdlet, function,
script". This prevented using a puppet.working_directory on Windows.
Merge pull request #4059 from brettporter/windows-puppet-wd

Unable to use puppet.working_directory on Windows