fix wrong assert in notify_ready_to_unpack

The offset will always be >=4 because we store the CellStatus in the
data sent to p4est in front of the user data. This means the smallest
offset will 4, no matter how much data is attached.
add test
add documentation to register_data_attach
Merge pull request #51 from tjhei/fix_data_attach

fix, test, document Triangulation::register_data_attach

 * fix a bug in an assertion
 * add a test
 * document how the CellStatus in the callback function works
Implement new initialize method for Trilinos AMG preconditioner: It can be based on an Epetra_RowMatrix object. We can use this code path for the standard initialize method with TrilinosWrappers::SparseMatrix as well.
simplify doxygen input path
reduce warnings from thousands to hundreds as long as major code is undocumented
fix displayed include paths in doxygen output
fix some of the warnings
Improve the documentation for the new initialize methods.
Patch by Alexander Grayver: Fix face interpolation between FE_Nedelec elements.

This patch fixes a bug in the FE_Nedelec::get_face_interpolation_matrix related to the wrong indexing of the DoFs located on element faces. This patch ensures that the code produces an interpolation matrix with full column rank meaning that all DoFs of the FE with lower order are constrained.
Merge pull request #53 from bangerth/fix-nedelec-interpolation-matrix

Patch by Alexander Grayver: Fix face interpolation between FE_Nedelec elements.

This patch fixes a bug in the FE_Nedelec::get_face_interpolation_matrix related to the wrong indexing of the DoFs located on element faces. This patch ensures that the code produces an interpolation matrix with full column rank meaning that all DoFs of the FE with lower order are constrained.
Merge pull request #45 from guidokanschat/doxygen_cleanup

Some cleanup of doxygen issues:
simplify doxygen input path
reduce warnings from thousands to hundreds as long as major code is undocumented
fix displayed include paths in doxygen output
fix some of the warnings
Merge branch 'master' of https://github.com/dealii/dealii
Correct return type of n_global_rows for 32 bit integers.
Improve documentation
List change in doc/news/changes.h
Merge pull request #52 from kronbichler/master

New initialize method for Trilinos AMG preconditioner with Epetra_RowMatrix