Support hotsync with on-the-fly definition of a node file

Example 1: create a node file on the fly, apply web role, and sync it to foo.example.com
pantry hotsync node foo.example.com --role web ...

Example 2: create a node file on the fly from a template, apply logging role, and sync it to foo.example.com
pantry hotsync node foo.example.com source.example.com --role logging ...