Complete development of miniAFQMC

[mmorale3]

Complete development of basic miniAFQMC for ECP milestone.
To do:

1. Complete documentation.
2. Clean distributed version:
   2.a incorporate mpi3.
   2.b replace boost::interprocess with mpi3:shm
3. Write report.

[mmorale3]

Now that the reimplemented AFQMC code is ready in QMCPACK, move changes to miniAFQMC.