made amuxCRS a template function with two template parameters - one for the floating point number type, the second for the index type

- added interface for erasing enties from the matrix (implemented asap)
- added interface for getting a column of the matrix (implemented asap)

a) added to class templates SparseMatrixBase and CRSMatrix another template parameter for index sets
b) added method getNNZ() to class template CRSMatrix

- removed unused class LinkedTriangle

- added test programm for solving a linear system with CG-method
- time measurement is at the moment OS dependent!
- added Base folder
- added GeoLib folder
- added files in MathLib folder - restructured MathLib folder

- applying changes to interfaces

* 'master' of github.com:ufz/ogs:
  readme test
  my initial contribution to OGS-6

git-subtree-dir: cmake
git-subtree-split: 2c1a3532

Updated README