Should reading <process>4</process> from the dimr_config be supported

[MRVermeulenDeltares]

What is the need for this task.
In #562 development was done to support the process for the dimr_config when generating the file from a model.
During the development the question arose "Should reading <process>4</process> from the dimr_config be supported".
The manual was not fully clear whether this is correct or not, thus this should be investigated further. It would mean to run on a single core, but not on the first one. The same question goes for <process>4 5 6 7</process>.

What is the task?
An investigation should be done to clear up if HYDROLIB-core should support reading <process>4</process> from the dimr_config be supported.

The expected outcome of this issue would be either a clear yes or no answer and a followup issue when needed.

@rhutten