Added optional output file name parameters.

examples/parameter_example.yml

@@ -34,6 +34,8 @@ Snapshots:
 # Parameters governing the conserved quantities statistics
 Statistics:
   delta_time:          1e-2 # Time between statistics output
+  energy_file_name:    energy # (Optional) File name for energy output
+  timestep_file_name:  timesteps # (Optional) File name for timing information output. Note: No underscores "_" allowed in file name 
 
 # Parameters for the hydrodynamics scheme
 SPH: