Adds comparison ops to proxied java.util.Map objects

Completes fix for http://bugs.jython.org/issue1631 by adding __le__,
__lt__, __gt__, __ge__ comparison operators. Now any proxied Map
objects are compared by their key sets for ordering
comparisons. Previously the default comparison was done, which is by
their class name (eg "HashMap") and then by
System.identityHashCode. (This default comparison is removed in Python
3.)

Note that when comparing java.util.Map objects with each other, Java
semantics apply. This means that keys are not converted to Python,
then compared. Likely the only scenario this comes up is creating a
Java Map from Python objects, specifically of int and long
objects, then doing a comparison. Example:

HashMap({1L:2L}) != HashMap({1:2})

but

HashMap({1L:2L}) == {1:2}

Supporting Python 3 will fix this problem by removing the distinction
between say 1 and 1L.