2.2-rc1

TRIQS Version 2.2.0 introduces substantial performance
improvements by reworking the array memory allocation and
by further changing the behavior of view types of arrays and
Green functions. The Release also introduces structural
changes to the mpi and itertools components to make them
usable as standalone components.
Beyond that, this release fixes several library issues and
improves the documentation. We provide a more detailed
description of the ChangeLog