Added support for Parallels Desktop for Mac [GH-223]

Added builder plugins: builder-parallels-iso and builder-parallels-pvm.
Added support for Parallels Desktop for Mac [GH-223]

Added documentation for Parallels builder.
Added support for Parallels Desktop for Mac [GH-233] in the vagrant post-processor.

The code originate from https://github.com/YungSang/packer-parallels
Added support for Parallels Desktop for Mac [GH-233] in the vagrant post-processor.

Fixes https://github.com/rickard-von-essen/packer-parallels/issues/3
Merge pull request #1101 from rickard-von-essen/parallels

Add support for Parallels Desktop for Mac [GH-223]