finish grid and mesh block

Usecases/README.md

@@ -133,11 +133,44 @@ In detail:
   might be an issue depending on your machine.
   >>>
 
-- `starttimes = {0: 0.0}` starttimes gives a list of starttimes to run the simulation from.
-  The list is looped over and a simulation is run with t_0 as initial time
-  for each element t_0 in starttimes
-- timestep_size = 0.001
-- number_of_timesteps = 20
+  - `starttimes = {0: 0.0}`: `starttimes` is a dictionary containing pairs
+  `t0_index: t0` specifying starttimes `t0` along with the number this start  time should be given `t0_index`. Usually you will want to have `t0_index`
+  set to zero because `t0` is the intial timestep.
+  However, if the simulation stopped for some reason and part of the data is
+  valid, a later time can be specified along with the index of the timestep
+  it had in the first attempt of the simulation.
+  >>>
+  **Example:** Say you wanted start
+  the simulation at `t0 = 0.5` and let that be the 87th timestep, you would set
+  `starttimes = {87: 0.5}`.
+  >>>
+
+  In case more than one element is given parallel simulations are started starting from the specified starttimes.
+  >>>
+  **Example:**
+  Assume `timestep_size = 0.01` and `number_of_timesteps = 50`
+  `starttimes = {
+    0: 0.0,
+    50: 0.5
+  }`
+  yields a simulation over [0.0,1.0] but split into to processes and saved into
+  two different folders.  
+  >>>
+  This is also usefull to test parameters if `number_of_timesteps = 1` and
+  the behaviour of the solver want to be tested at various timesteps one
+  could set up an example as
+  ~~~python
+  starttimes = {
+    0: 0.0,
+    1: 0.5,
+    2: 1.0
+    3: 1.5
+  }
+  ~~~
+  to test the behaviour of the solver at different times.
+
+- `timestep_size`: Set size of the timestep.
+- `number_of_timesteps`: Set numbers of timesteps to calculate.
 
 ### LDD SCHEME PARAMATERS
 ~~~python