Provide a help for each of the patterns #15
Description
Now with the ptrnarg option available, we can provide at least a help message for each pattern even if the pattern doesn't accept any ptrnarg.
For example, if the user uses the simulator like this:
./orcs -i infile.dot -p gather -a help the simulator could print the help message that is available in the documentation and exit:
In the gather pattern a single node receives a message from all other nodes in the communicator. This pattern consists of a single level.
Functionality for help/error messages in the patterns is already in place. We just need to provide the help messages.