mosfet_3d dev'ing/pimped linear_solver/added debug output

. added timer class which prints tiings for each step of a
  nonlinear solver step
. added viennacl_support.hpp to print conveniently the available and
  current devices on the system
. mosfet_3d: used same setup as in ViennaSHE device, for a still
  unknown reason it still does not converge