add optional uri references to the DNAComponent #29
Description
a) uri to a model specification (Deepak, Chris, Herbert, Jean, Mandy)
b) uri to experimental data, includes sample location (Doug, Cesar, Jean, Mandy)
c) uri physical assembly information (Doug, Cesar, Jean)
d) uri to a visualization format, cf. TinkerCell, iBioSIM, Clotho (Deepak, Herbert, Chris, Doug, Jean, Mandy)