[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