Elasticity example in Examples/ADMFD/elasticity.cpp

Bug fix - when assigning a matrix with different storage container, the
number of rows and columns is changed after the assignment itself,
which leads to incorrect behavior of opeartor(i,j) of the matrix.

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.

cavity and backward facing step

introduced in previous commit

mpi.h included after stdio.h

fixes in ADMFD

Add Examples/ADVDIFF example for advection-diffusion

Add exotic grid generators to Examples/GridTools

Add Examples/TestSuits for tests of diffusion and advection-diffusion
problems

DrawGrid -> DrawGridTests

Cell size is determined in projection of velocity for streamlines

Sparser streamline placement

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