Static variable improvements

[devinrsmith]

package com.example;

public class MyClass {

  public static final int FOO = 1;

  public static int BAR = 2;
}

jpy currently only maps final static variables for getting; we should be able to get static variables that are not final.

jpy currently does not allow setting static variables. (Easy to see there are no calls in this code base to SetStaticField Routines)

import jpy

_JMyClass = jpy.get_type("com.example.MyClass")

# works
foo = _JMyClass.FOO

# does not work
bar = _JMyClass.BAR

# does not work
_JMyClass.BAR = 42

Related to #191

[devinrsmith]

You can potentially work around this with reflection:

import jpy

_JMyClass = jpy.get_type("com.example.MyClass")

# workaround
bar = _JMyClass.jclass.getField("BAR").get(None)

# workaround
_JMyClass.jclass.getField("BAR").set(None, 42)