Improve error message when the number of element blocks is exceeded

[ktbolt]

The solver partitions the mesh into blocks for parallel solution. When the number of element blocks is large than the default (5000) an error message is written explaining to increase the number of processors.

The error message is not too helpful it seems, several users have posted to the Forum asking why the simulation failed.

I'll improve the error message to make it more meaningful and also suggest the number of processors needed to run the job.