[Users] GRHydro changes to be merged into trunk

[Christian D. Ott]

Hi All,

later today, we will merge the current development branch with the
trunk branch of GRHydro.

Major changes:

 * GRHydro now knows about electron fraction and temperature and can
   handle finite-temperature EOS. In order to use this feature, you
   have to set: hydrobase::temperature_evolution_method = "GRHydro" and
   hydrobase::y_e_evolution_method = "GRHydro". In addition, you'll of
   course need a hot EOS (see below) and appropriate initial data.

 * GRHydro now uses EOS_Omni. The EOS_Base dependence has been removed.
   You will need to change your parameter files and activate
   EOS_Omni which will be moved to the EinsteinEOS arrangement today.
   Example parameters for a TOV NS evolution are:
   eos_omni::poly_gamma                    = 2.0
   eos_omni::poly_gamma_ini                = 2.0
   eos_omni::poly_k                        = 100.0
   eos_omni::gl_gamma                      = 2.0
   eos_omni::gl_k                          = 2.0

   EOS_Omni currently supports a polytropic EOS, a gamma-law EOS 
   (this is what we used to call "ideal fluid" EOS), a hybrid EOS
   (a hot 2-piece polytrope), and nuc_eos, which can handle hot
   tabulated EOS. Tables for the latter can be obtained from
   http://www.stellarcollapse.org/microphysics. This currently
   works well for core collapse, but has not been tried for NS
   evolutions. When using the nuc_eos routines, please make reference
   to http://iopscience.iop.org/0264-9381/27/11/114103 .

 * GRHydro currently still supports the second legacy EOS interface
   "EOSG_Base", but this support will be removed soon to simplify the
   code.

Please let me and Frank Loeffler know if you have any concerns about
the above.

Best, 

 - Christian Ott
 for the Einstein Toolkit maintainers.