Change the default so that NBFIX amber topology files use a long-range
correction by default. Then add a test for using the long-range correction and
_not_ using the long-range correction.  Comment out the test using the
long-range correction since it currently segfaults.  When the fix for the
segfault is added, this test can be reinstated (but the energy has to be
updated)

This change in default makes it consistent with the default behavior for the
classical NonbondedForce, and I would have set that as the default to begin with
if I had known it was supposed to work.
Update the energy in anticipation of just uncommenting that test when the fix is
added.
Merge pull request #530 from swails/longrange

Update default long-range option and expand test