* implement default ctor, users were relying on the compiler generater one and reported issues on the forum
* turns out that we crash on 1x1 matrices but work on Nx1. No interest in fixing that, so just guard by assert and unit test.
few bits left of the comma and for floating-point types will never return zero.
This replaces the custom functions in test/main.h, so one does not anymore need
to think about that when writing tests.
- the decompostion code has been adfapted from JAMA
- handles non square matrices of size MxN with M>=N
- does not work for complex matrices
- includes a solver where the parts corresponding to zero singular values are set to zero
