Support method parameter names, if available; small bugfix to exception handling.
Method parameter names are now available using MethodInfo#getParameterNames(), if available (this requires the code to be compiled with JDK8 or above, with the -parameters commandline parameter provided to the javac compiler). The parameter names will also be included in the human-readable string representation of the method signature given by MethodInfo#toString(). Thanks for @dantesun for the request (fixes #146).
Also fixes exception handling for cleaner shutdown in case of an exception while scanning.