Corrected issue with RFFT APIs
Added some features to compute graph
Improved documentation related to RFFT
Changed how Python wrapper is built (to prepare fro future
evolution).
The compute graph hierarchy (Python and C++) has been modified.
It will break the code using the CG and the include and import will
have to be modified.
New function prepareForRunning is needed in CG nodes even if not used in
static mode. Without this function, code using compute graph won't build.
Christophe Favergeon