Only MPICommunicator and DistributedGrid is implemented.

Allow existance of non setup synchronizer object. MeshFunction creates grid synchronizer automagicli with binding.
(only if distr grid was chnged)

Implementation of TimeIndependentPDESolver.

There is shor test of this stuff for 1D 2D and 3D.

Relpaced tabs with 4spaces.

- used variadic templates to avoid code bloat
- added execHost static method to avoid nvcc warnings

- separate data types for input arrays of binary operations
  (necessary for the equality comparison of two arrays of different
  type)
- added separate template parameter for ResultType, which defaults to
  the RealType
  (the goal is to allow sum of bool vectors into int instead of bool)