Added edge and node types to conformity
Added create and destroy calls to all darcy traversals as well as further edge and node types
Added create and destroy calls to all swe traversals as well as further edge and node types
Changed tag upper bound to 2^28 - 1 for compatibility with MPICH 3. Added serial midpoint cutoff to load balancing (not yet callable though). Also changed send and receive to transmit only non-empty data
Fixed a small memory leak - grid%destroy() must be calle din parallel in order to free thread data
Changed adaptive traversal to allow edge and node types, fixed a bug taht would always ignore edge types and added edge and node types to linear solvers