Restore users ability to set App.name

In previous releases I introduce the option for user to rename an App with a custom name, that can show up in logs, or summarize.
You removed this, and I would like to re-introduce it, but without the @property stuff.
App should init with required arg "appname" and could accept an optional parameter name.
appname is the first and only required parameter for App to work. Users will never use something like app = App(appname=...), and should use app = App(appname, "image.tif", ..., name="Custom").
appname would be the default name if no custom value is provided :

App.name = name or appname

Because for now, it is not right even if user can force app.name = , it occurs too late and won't show in logs.
Moreover it does not work for internal object functions.