Add default zar.json template file
zpm,test_zpm: move default zar.json->template file

This moves the default zar.json contents from a dictionary in the code
to plain file in the zpmlib/templates/ directory. There are other
similar templates already here, so this seems to be a better place for
it. It's also easier for a user to find, since they don't have to dig
through code to get it.