correlated RB fitter

[dekool]

integrating @dcmckayibm correlated RB code into ignis.

before merging we need also to:

• add noisy tests to ignis
• add function to generate new data for the test
• adjust the code with the refactor of RB (after merging PR Refactor RB code to use the new Clifford operator class and update the CNOTDihedral class #407 )

Fixes #413

[ShellyGarion]

close #413

[dekelmeirom]

found and fix the bug which caused wrong results in cases of pattern with different sizes of subsystems.
the bug was due to reading the the bits representing the subsystems from right to left instead of left to right when calculating the Z-correlators. this caused the calculation of the correlators to be based on results of wrong measurements interpretation.

• note: the bug was visible on patterns without 'right-left symmetry' (and not on patterns with different subsystems sizes like I first thought)

[mtreinish]

Active feature development has ceased on qiskit-ignis as the project is deprecated and most of the work has moved to qiskit-experiments. As such I'm closing this PR.