This a lightweight pack-unpack class holding two vectors.

This helps with generalization when using essentially same concept of addition.

This simplifies matrix construction in many places because in many cases we need just a bilinear form.

fix getMaxDiagCoeff() in LisMatrix. prepare a diagonal vector by ourself...

Fix lis matrix get max diag coeff

Testing multiple build runs on travis.

Update Doxyfile.in to 1.8.4 version.

Updated with 'doxygen -u'.

Speed up Mesh::removeUnusedMeshNodes() a bit.

Bug fix for axis aligned bounding box class AABB.

add tests for Lis vector, matrix and linear solver

Delete SystemOfLinearEquations / Add Lis version of matrix, vector and linear solver tools

Add lis matvec solver - some improvements/changes/stuff to discuss

- Removed the update code for calculation of _max_diag_coeff from
  + LisMatrix::setValue()
  + LisMatrix::addValue().
- Removed the _max_diag_coeff attribute.
- Implemented the functionality in LisMatrix::getMaxDiagCoeff().

- Reformatted code
- Made docu more meaningful
- Changed name of first parameter of constructor
- Moved implementation of setValue() and getValue() from header into cpp-file