A new timestepper that reads timesteps from a file generated using
ecl_summary "DECK" TIME
and applies it to the simulator
Also a parameter timestep.initial_step_length (default 1 day) is added
to controll the frist timestep.
Have removed the SimulatorState base class, and instead replaced with
the SimulationDatacontainer class from opm-common. The SimulatorState
objects were typcially created with a default constructor, and then
explicitly initialized with a SimulatorState::init() method. For the
SimulationDataContainer RAII is employed; the init( ) has been removed -
and there is no default constructor.