Assembler for global basis transfer matrices

The method assembles the transfer matrx between fine and coarse grids.
Assumptions are
 - the grids are related but not necessarily direct descendants
 - the global dune-functions basis are scalar, i.e., leaf nodes in the basis tree

For evaluating local functions on other geometries a small wrapper is written.
For chaining sequencial father geometries another small wrapper is written.

Two unit tests:
- first, test wether the transfermatrix interpolates coefficients from corase to fine
  for lagrange basis
- second, test wether a jump over two grid levels can be reproduced by two simple transfers