Added createUnmanagedPackage target and call at start of deployCI

This should allow deployCI to be run against an org which does not already have the cumulusci.package.name unmanaged package created.  The createUnmanagedPackage target deploys an empty directory with a package.xml which contains only the apiVersion and the fullName of the package.

# Warning
# Info
* You no longer have to manually create the unmanaged package before running deployCI.  The package will be automatically created in the target org if it does not exist
# Issues
Fixes #9