qmca doesn't do weighted average

```
$ cat qmc_short.s000.scalar.dat
# index LocalEnergy LocalEnergy_sq LocalPotential Kinetic ElecElec IonIon LocalECP NonLocalECP BlockWeight BlockCPU AcceptRatio
0 -2.1497437216e+01 4.6296784906e+02 -4.1747444816e+01 2.0250007600e+01 -5.8015375457e+00 -2.5551326901e+01 -1.1200609672e+01 8.0602930218e-01 3.2000000000e+01 1.6943663359e-03 7.9785156250e-01
1 -2.1533011570e+01 4.6433605720e+02 -4.0404599724e+01 1.8871588154e+01 -5.9175158025e+00 -2.5551326901e+01 -1.0918284006e+01 1.9825269859e+00 1.2000000000e+01 1.7340630293e-03 7.7929687500e-01
$ qmca -q ev -e 0 qmc_short.s000.scalar.dat
LocalEnergy Variance ratio
qmc_short series 0 -21.515224 +/- 0.012577 0.746756 +/- 0.057478 0.0347
```
qmca only does `(-2.1497437216-2.1533011570)/2 = -2.1515224393` but to me a weighted average is more appropriate.

I expect `(-2.1497437216 * 32 -2.1533011570 * 12)/(32+12) = -2.1507139312`