A command is a scripted method or compiled command class implementing a
specified method signature. Commands are loaded from the classpath and
may be imported using the importCommands() method.
This method searches the imported commands packages for a script or
command object corresponding to the name of the method. If it is a script
the script is sourced into this namespace and the BshMethod for the
requested signature is returned. If it is a compiled class the class is
returned. (Compiled command classes implement static invoke() methods).
The imported packages are searched in reverse order, so that later
imports take priority. Currently only the first object (script or class)
with the appropriate name is checked. If another, overloaded form, is
located in another package it will not currently be found. This could be
fixed.