Add GPU pyfaust.Faust wrappers for transpose, conjugate, pruneout.

Refactoring TransformHelper getNbRow/Col into parent TransformHelperGen

Other minor unrelated changes:
- pyfaust.Faust.size doc update.
- Fix conjugate decl./def. in faust_linear_algebra.hpp
- Use FAUST_PRECISION instead or raw-coded value in TransformHelper<FPP,Cpu>::normalize().