E. da Cunha, F. Walter, I. Smail, M. Swinbank, J. Simpson, R. Decarli, J. Hodge, A. Weiss, P. van der Werf, F. Bertoldi and 8 other author(s). (2015)cite arxiv:1504.04376Comment: 22 pages, 14 figures, 2 tables. Accepted for publication in the Astrophysical Journal. The new MAGPHYS model libraries used in this paper will appear in www.iap.fr/magphys. The SMG SED templates shown in Section 6.1 are available at http://astronomy.swinburne.edu.au/~ecunha/ecunha/SED_Templates.html.