Update error message for SVDLIBC to check that it's installed

[davidjurgens]

When the SVD driver can't find the SVDLIBC executable, it usually has a message like "java.io.IOException: Cannot run program "svd": error=20, Not a directory" in the Throwable. It would probably help the end user's if we caught the exception, looked at the message and tried reporting something more reasonable (e.g., "couldn't find the executable") so they could try debugging on their own, rather than propagating the IOException to the top and having them wonder what went wrong.