Make the text about "application independence" generally applicable
    
    The existing text had a very narrow scope: packages that contain a
    .desktop file that does not have the line `+NoDisplay=true+`. But the same
    rule applies to pretty much everything.
    Let's change "application" to "package" to generalize this.
    
    Also, a text which specifies when Recommends and when the other dependency
    types should be used is added.
    
    This partially answers the question about "modularity" (in the sense
    of package independence) raised in https://pagure.io/fesco/issue/2040.