Fix compilation issue with std::isinf

Finish memory_pool implementation in container.h

Use of matrices allocated in memory pool for intermediate results in
dense linear algebra operations in inmost_dense.h

Use of memory pool for matrices in inmost_autodiff.h

Change error reporting and return type in Invert, Solve,
CholeskyInvert, CholeskySolve, PseudoInvert, PseudoSolve

Add unit tests for linear algebra on dense matrices.

The class ConstSubMatrix is used to access a submatrix of a const
matrix with (i1,i2,j1,j2) operator.

Additional updates to template handling in AbstractEntry::Access, fix a bug in thread_private class with openmp

thread_private class for static OpenMP objects acts as iterator

EndModification do not unnecessarily delete orphan elements

Fixed Face::getNodes behaviour inside BeginModification and
EndModification region (same fix as in andre_brench)

Added template access functions for AbstractEntry class, allows to get
(matrix of) values, unknown indices or unknowns themselves depending on
template parameter

Examples/OldDrawGrid:
* Adjustments for svg output of color gradient in color bar (previously
was not properly working in Inkscape)
* Preparations for isosurface extraction code

Thanks to Matvey Kraposhin

not tested yet

PrepareReceiveInner was not called for sparse tag

Possible fix in packtagdata/unpacktagdata - mismatch between amount of
calls to MPI_Pack and MPI_Unpack

GridTool for Kmeans clustering, should eventually move to Partitioner
class

Fix ambiguity complains in autodiff with g++-4.2.1; disable extended solver tests that require matrix collections

Fix binary heap with key update in maximum product transversal
algorithm in inner solvers.

Correct global rescaling strategy in MLMPTILUC2 inner solver.