Feature/nothrow

There should be an option to not abort the program from within the library. This is not such a problem for C++ code which can just catch exceptions. (We should document which functions can throw which exceptions!)

However, the Fortran interface does not provide such features. So the proposal is to set an error number ALL_errno and description string ALL_errdesc = e.what() that can be queried for successful execution.

This is then provided by an additional error argument to the Fortran functions, as well as a function to query the error number and describing test explicitly.

This is necessary at least for signalling domains that do not satisfy the minimum domain size requirement.