Implement a newmark scheme for the state

src/Makefile.am

src/compute_state_dieterich.hh

src/compute_state_dieterich_common.cc

src/compute_state_dieterich_common.hh

src/compute_state_dieterich_euler.cc

src/compute_state_dieterich_euler.hh

src/compute_state_dieterich_newmark.cc

src/compute_state_dieterich_newmark.hh

src/one-body-sample.cc

src/one-body-sample.parset