- it is sensible to filter by default, however, it turned out that on some complex models Elmer fails to compute if the mesh volume regions are too small (in most cases) or at a certain mesh region. By disabling the filtering, one gets at least for the latter case a visual feedback where the mesh volume of the different CPU are (by also setting a transparency to the result pipeline).
- the code already assured that the number of used CPU cores for Elmer can only be > 1 if a valid path to the '_mpi' executable is specified. However, we can have the case that Elmer was uninstalled, then the path validity checker returns an empty path and then the check for the number of cores but handle this case. THis PR does exactly this.
- also fix typos and improve error message
- also add missing save guard for hardware check
- this needs proper testing, especially on a non-Windows system
- note that for some tasks multi-threading requires non-standard additional solvers like MUMPS. Ideally the user should be informed about this, depending on the equations he uses. But this should not block this PR, meaning to use multi-threading in general.
- currently one can enter any path for the solver executables, a check is missing
- moreover for Z88 the executable name is error-prone (just happened to me and cost me half an hour to find out what is wrong), therefore check also the correct filename. For Elmer this cannot be done since there are different executables one can choose of (e.g. for multi-threading etc.)
