+Add MOM_EOS_Roquet_SpV.F90

  Added the new equation of state module MOM_EOS_Roquet_SpV with the polynomial
specific volume fit equation of state from Roquet et al. (2015).  This equation
of state has also been added to MOM_EOS, where it is enabled by setting
EQN_OF_STATE="ROQUET_SPV".  Two other new valid settings have been added to
EQN_OF_STATE, "ROQUET_RHO" and "JACKETT_MCD", which synonymous with "NEMO" and
"UNESCO" respectively, but more accurately reflect the publications that
describe these fits to the equation of state.  The EoS unit tests are being
called for the new equation of state (it passes).  By default, all answers are
bitwise identical, but there are numerous new publicly visible interfaces.