Generate multiple states per realization by flipping random spins after each simulation
Generate multiple states per realization by flipping random spins after each simulation

* Added multistate support for quick overview
* Truncate less when randomizing into new state
* Generate up to 8 states
* Speed up of multitheta contraction
* Apply sz pauli operator in randomization instead of sx
* Apply prod sx + prod sz instead, to make sure that entanglement structure is modified
* Measure entanglement difference between successive states on single realizations


Former-commit-id: 8f4e68d55897cd19cfacb0f3ee2608b5f006c0ce
DavidAce/DMRG,DavidAce/DMRG,DavidAce/DMRG,DavidAce/DMRG