`fdroid update --create-metadata` now outputs YAML format
`fdroid update --create-metadata` now outputs YAML format

As part of the push towards using YAML as the main metadata format, this
makes the blank template be a .yml file.

f-droid/fdroid-server,f-droid/fdroid-server,f-droid/fdroid-server,f-droid/fdroidserver,f-droid/fdroidserver,f-droid/fdroidserver,fdroidtravis/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroid-server,f-droid/fdroidserver,f-droid/fdroid-server,fdroidtravis/fdroidserver,f-droid/fdroidserver,fdroidtravis/fdroidserver