Started looking at a more flexible large deformation interface
Added some pseudo code and alternative methods for giveInternalForcesVector and  computeStiffnessMatrix
incremental changes
incremental changes
Added method for computing effective stiffness but something is wrong in the expression. Also internal force vector differs for nlgeom = 1,-1 - different initial stresses
New code reproduces same result as with nlgeom = 1

Need to clean up now
Added method to reduce a full strain matrix to vector form. Maybe it should be placed under structural elements instead.
Added support for storing the deformation gradient in the material status for all structural elments.
Belonged to the previous commit
Modifications to the structure of large deformation analyses. Only works for full 3d Mat mode for now.

Have removed the need for element to implement NLBmatrix but the need to implement the BFmatrix
Added Deformations gradient as an IST for export
Added computeBHmatrixAt
Fixed bug when checking size
Updates regarding large deformations
Some tidying up in nlstructural element, nlgeom=1 will now call the new code
Added computeBHmatrixAt in almost every class that implemented computeBFmatrixAt. The new method should produce the same as matrix as BFmatrix but uses the standard OOFEM ordering instead of column wise ordering. These methods have not been checked yet.
Interface for large deformations based on S:E seems to be working
Merge branch 'master' of git://github.com/Micket/oofem
Started to add support for large deformations based on first PK stress and the deformation gradient.

Many methods needs to be updated so they can handle reduced cases such as plane stress etc.
Added first Piola-Kirchhoff stressVector in structuralMaterialStatus