builder/parallels: Bundle python version of prltype

Uses the Python API from Parallels Virtualization SDK to write
boot commands.

This eliminates a 3rd party requirement and makes it easier for people
not using homebrew to get started with packer.
Update CHANGELOG.md
Merge pull request #1499 from JessThrysoee/python_prltype

builder/parallels: Bundle python version of prltype