[bugfix,documentation] spelling
[FEATURE] Add UMFPack support to dune-istl

This commit contains
- a wrapper for the C library UMFPack
- tests for both CMake and autotools to find UMFPack on the system
- a unit test for UMFPack
- a new MatrixType ColCompMatrix which is a base class for a column
  compressed matrix. SuperLUMatrix now inherits from this base class.
  This way, no code is duplicated for the very similar interface in
  UMFPack.
- the SuperLU-specific part of OverlappingSchwarz code is abstracted
  to work with either SuperLU or UMFPack
[overlappingschwarz] Also test DynMatrixSubdomainSolver
[amg] Use UMFPack as a direct solver if available.

This is supposed to be a temporary hack. If Umpack is available
the it is chosen of SuperLU. Otherwise SuperLU is chosen if it
is available.
prevent umfpack from using wrong constructor when calling with superlu constructor list
Revert "prevent umfpack from using wrong constructor when calling with superlu constructor list"

This reverts commit 5336f23b950e9f1b5b8a51cdc103142ab47a779e.
add a compatibility constructor to make switch from superlu convenient
fix broken attempt at constructor delegation
[bugfix] make UMF_Info arrays local to not screw multithreaded computation
[bugfix] UMFPack should work without SuperLU around
[style] mark virtual methods as such in inherited class
[cleanup] remove verbosity code not functioning put into comments in 2010
[bugfix] free memory correctly when using decompositions loaded from file
Get rid of warnings.
[Bugfix] avoid bool mat_is_loaded from being potentially unintitialized
add name to COPYING
implement a dummy 'post'

now the preconditioner can be used in a Dune::Preconditioner context
[umfack] Moved build system tests for umfpack to dune-common

This patch removed the tests for umfpack from dune-istl as they
are already needed in dune-common. There are modules using umfpack
that do not require dune-istl. Therefore dune-common seems to be the
more appropriate place for the test.
Refactored smoothing code for better reuse.
Added algebraic twolevel method.

With this addition it is possible to construct a twolevel method by
specifying a fine level smoother (e.g. SeqOverlappingSchwarz), a
policy for the grid transfer, and a policy for constructing the
coarse level solver.