Enhancement: Print elapsed time, estimated end time during simulations

[megies]

I think it would be a nice enhancement to add a bit more information output during simulation runs.. regularly SW4 is printing lines like:

Time step     201  t =   6.5829694e-01

I think it would be nice if SW4 printed the elapsed run time so far (like it prints the total elapsed time at the end) and also a projected end time (based on the percentage of executed time steps so far) when it prints this line. Both only if it's feasible and not too much work, obviously.