Rename properties within which media content is referred

[blcham]

I assume that we support two forms how to address content:

ex3:q-with-media-444 :has-media-content "http://mediacms/media/path/to/media/user/username/hash_asset1.jpg" .

:asset-1 a :asset ;
    :has-source "http://mediacms/media/path/to/media/user/username/hash_asset1.jpg" ;
    :has-annotation 
              :annotation-polyline-1 ,
              :annotation-text-1 .
...
ex3:q-with-media-444 :has-media-content :asset-1 .

To me it does not make sense to reuse same property. Could we change 2) case to have :has-media-asset instead of :has-media-content ? I.e. it would be :

:asset-1 a :asset ;
    :has-source "http://mediacms/media/path/to/media/user/username/hash_asset1.jpg" ;
    :has-annotation 
              :annotation-polyline-1 ,
              :annotation-text-1 .
...
ex3:q-with-media-444 :has-media-asset :asset-1 .

Originally posted by @blcham in #442 (comment)