Terminate solves cleanly based on Postprocessor values

This implements the change proposed in #3735. The ```UserObject``` to trigger the termination based on ```Postprocessor``` values is part of the phase_field module. 
The test was adapted from the SplitCHMath test (which this test also used
before I moved it out of pf). I'll address those points after lunch.
 On Aug 15, 2014 12:36 PM, "Derek Gaston" <notifications@github.com> wrote:

> In test/tests/userobjects/Terminator/tests:
>
> > @@ -0,0 +1,10 @@
> > +[Tests]
> > +  [./test]
> > +    type = 'Exodiff'
> > +    input = 'terminator.i'
> > +    exodiff = 'out.e'
> > +    abs_zero = 1e-09
>
> 'abs_zero' shouldn't be necessary
>
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> <https://github.com/idaholab/moose/pull/3739/files#r16307872>.
>