Implement clone command to clone a PDK project #49
Description
At the moment it's a difficult process for a user to clone a project, let's make it a bit easier!
This should be a standard git clone of the project files (including the etc/channels.xml?).
It should also set this up as a git remote called origin for future pulls.
The pdk download and pdk repogen commands will then download debs from our repo when needed.