Added YAML file for uniform DM box example.

examples/UniformDMBox/uniformBox.yml

+# Define the system of units to use internally. 
+InternalUnitSystem:
+  UnitMass_in_cgs:     1   # Grams
+  UnitLength_in_cgs:   1   # Centimeters
+  UnitVelocity_in_cgs: 1   # Centimeters per second
+  UnitCurrent_in_cgs:  1   # Amperes
+  UnitTemp_in_cgs:     1   # Kelvin
+
+# Parameters governing the time integration
+TimeIntegration:
+  time_begin: 0.    # The starting time of the simulation (in internal units).
+  time_end:   1.    # The end time of the simulation (in internal units).
+  dt_min:     1e-6  # The minimal time-step size of the simulation (in internal units).
+  dt_max:     1e-3  # The maximal time-step size of the simulation (in internal units).
+
+Scheduler:
+  max_top_level_cells: 8
+  cell_split_size:     50
+  
+# Parameters governing the snapshots
+Snapshots:
+  basename:            uniformDMBox # Common part of the name of output files
+  time_first:          0.           # Time of the first output (in internal units)
+  delta_time:          0.01         # Time difference between consecutive outputs (in internal units)
+
+# Parameters for the self-gravity scheme
+Gravity:
+  eta:                   0.025    # Constant dimensionless multiplier for time integration. 
+  theta:                 0.7      # Opening angle (Multipole acceptance criterion)
+  epsilon:               0.00001  # Softening length (in internal units).
+  
+# Parameters governing the conserved quantities statistics
+Statistics:
+  delta_time:          1e-2 # Time between statistics output
+
+# Parameters related to the initial conditions
+InitialConditions:
+  file_name:  ./uniformDMBox_100.hdf5     # The file to read