Merge branch 'master' into L2SDP-885b

applications/lofar2/model/pfb_os/dsp_study_erko.txt

...ons/lofar2/model/pfb_os/filter_design_windowed_sync.ipynb

applications/lofar2/model/pfb_os/pfb_reconstruction.ipynb

applications/lofar2/model/pfir_coeff.m

applications/lofar2/model/rtdsp/firfilter.py

applications/lofar2/model/rtdsp/fourier.py

applications/lofar2/model/rtdsp/plotting.py

doc/erko_howto_tools.txt