Changes:

- Add new backends: lfilter (using transfer functions to decouple xi into its elements, then scipy lfilter per element) and cupy (using CPUs & CUDA, if available)
- Add generalization to more than 1 dimension (NDCompositeCosts) and corresponding backends
- Add new polynomial ALSSMs (Legendre and Meixner)
- Add new steady state calculation methods
- Add new minimization method
- Add rls.fit() and rls.convolve() as collection-functions
- Add new examples
- Switched docu to mkdocs
- Update API of trajectories and windows

Update conf.py

update version

Merge branch 'dev'

Update setup.py

version update