v1.9.0

• Adjoint solver to compute sensitivity of solution to material perturbations (#795).

• Experimental do_averaging feature for user-defined material functions (#771, #791).

• Periodic boundaries support in near2far via nperiods option (#769, #789).

• Capture more output in Python notebooks (#785, #807).

• dft-energy feature (#744, #747).

• Eigenmode sources are normalized to unit power (#728).

• Fix interpolation of DFT slice output (#787).

• Bug fix in run-k-points (#779).

• Eigenmode sources for negative angles (#752).

• Various other minor bugfixes, build fixes, documentation improvements, tutorials, etcetera.