reorg `fdroid server` to allow for multiple server types
reorg `fdroid server` to allow for multiple server types

Right now, ssh+rsync is the only supported server upload type.  Things like
cloud storage services are useful storage bins for fdroid repos since they
are often not blocked while specific websites like Google Play are.

OneEducation/AppUniverse_Server,fdroidtravis/fdroidserver,f-droid/fdroid-server,fantastico/fdroidserver,f-droid/fdroidserver,OneEducation/AppUniverse_Server,f-droid/fdroidserver,matlink/fdroidserver,f-droid/fdroid-server,fdroidtravis/fdroidserver,f-droid/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroidserver,fantastico/fdroidserver,f-droid/fdroidserver,matlink/fdroidserver,fantastico/fdroidserver,f-droid/fdroid-server,matlink/fdroidserver,f-droid/fdroid-server,f-droid/fdroid-server,OneEducation/AppUniverse_Server,fantastico/fdroidserver,fdroidtravis/fdroidserver,fantastico/fdroidserver,OneEducation/AppUniverse_Server,matlink/fdroidserver,OneEducation/AppUniverse_Server,matlink/fdroidserver