qmcpack/tests/heg/heg_54_J2rpa

This test is to be used to resurrect the two-body RPA Jastrow.
The RPA Jastrow was used in the original test set for QMCPACK (circa 
2008) and it has been broken in QMCPACK since at least 2010.  Recent 
efforts were made (2016) to resurrect the RPA Jastrow, but the current 
test case results in an unphysically high energy and variance.  The 
current test is intended for developer use only and not as a test of 
the correctness of the current code.  As such it should not be run 
in the e.g. nightly tests until the issue is fixed.

The test is for a 54 electron HEG in 3D at rs=5.0.  A two-body 
Gaskell RPA Jastrow factor is used, including both short and long 
ranged parts.  The original output data includes results for VMC 
and RMC, though only the VMC inputs are used for the test at this 
time.  All of the original test files are included in ./qmc-ref.

The total energy used in this test was obtained from the original 
data with qmca:

>qmca -q e -e 2 qmc-ref/*s001*scalar*
qmc-ref/HEG.rs5.rpa  series 1  LocalEnergy = -4.209725 +/- 0.012941
  
The original scalar files do not contain the square of the local 
energy, precluding a test of the variance.