run.host_parameters are defined in Simulator instead of Host
Host#host_parameter_definitions are updated when status is changed into :enabled. Simuator#default_host_parameters[host_id] are deleted when the host is destroyed or when the host status is changed into :disabled
various refactoring for Default host parameter on simulator #287
change a method name in Simulator model
remember host paramter values in web form
implementing default value of MPI and OMP
add specs for SimulatorsController#_default_mpi_omp
add spec for Run#update_default_host_parameter
update default_mpi_procs and default_omp_threads

- when run is created, update default_mpi_procs and default_omp_threads
  of the simulator
trivial refactoring
refactoring
callback Host#delete_default_parameters_from_simulator
changed the order of fileds
Merge pull request #287 from crest-cassia/default_host_parameter_on_simulator

Default host parameter on simulator