Patch for JMX-16 by Michael Nussbaum.
patch by Chris Jeris for JMX-6
patch by Jürgen Hötzel for JMX-7
By default the invoke fn will pick the first jmx method signature that it finds. This is normally fine, but in the case of overloaded jmx methods may not be correct. This patch keeps the default behavior of the invoke method but allows for specifying a cusom method signature in the case that an overloaded method needs to be invoked.