Revisiting the evolution eigensolver.
Revisiting the evolution eigensolver. This commit contains few bugfixes :
- The Taylor expansion for imaginary time was not correct.
- The code was wrongly mixing the density between timesteps of the evolution
- The code was doing a subspace diagonalization which is not correct
- The orthonormalization routine was not stable and is replaced by the standard orthogonalization.
- The code was freezing states once converged, which is not correct unless independent particles
Besides this, the code now check that the exponential is stable. The default time-step is set to a valid close to the one shown in the litterature.
Revisiting the evolution eigensolver to make it working.
- I have checked that my code follows the Octopus coding standards
- I have added tests for all the new features added in this request.