Add Feature director:except with documentation and test case

See Doc/Manual/Java.html, 24.5.7 Java Exceptions from Directors,
for details on usage.  Basic functionality allows a director:except
feature to be added to a director method to add a manually written
handler to map java exceptions back to c++ exceptions.  Alternatively,
use new "directorthrows" typemaps to automatically generate handler
blocks for methods in a fashion analogous to the "throws" typemap.