Port KSpread's eigen1-based code to eigen2.
(That is just the matrix math functions: MINVERSE,...)

Unit-tests pass, but I can't find a way in the GUIto use the matrix-returning functions such as MINVERSE.
Strange.

Also, in the documentation, no function is described as returning a matrix.
I mean that in functions/math.xml, e.g. for MINVERSE, we have <Type range="true">Float</Type> but still in the GUI Help MINVERSE is described as returning a single floating-point.

Another minor complaint: MUNIT is very poorly named, it is not called the "unity matrix" but rather the "identity matrix", so I would suggest the name MIDENTITY.

Not sure though if I am allowed to make that kind of change, perhaps that is an ODF standard or something, I don't know.