Challenges and opportunities for NMR calculations: general discussion by Ashbrook, SE, Beran, GJO, Blahut, J, Blanc, F, Brammer, L, Brough, H, Brown, SP, Bornes, C, Charpentier, T, Dracinsky, M, Dudek, MK, Emsley, L, Fellowes, T, Gervais, C, Griffith, KJ, Griffin, J, Goward, GR, Hodgkinson, P, Hughes, CE, Hope, MA, Köcher, SS, Laurencin, D, Li, Z, Lill, SON, Morris, AJ, Mueller, LJ, Price, SL, Yates, JR