add worldcomm in evaluate function of Cst class (needed to call evaluate() on a constant expr)
Merge branch 'develop' of https://github.com/feelpp/feelpp into develop
add a parameter to indicate if all processors write a file or not (by default all procs write a file)
add options to generate file(s) to have the system memory evolution in function of number of RB elements (offline step)
Merge branch 'develop' into feature/rbframework