Daskification task chunked filtering and downsampling

Closes #162

New modules for filter infrastructure

• fir_filters_numpy FIR filter functions operating on whole numpy arrays, classes to define filters and boundary handling. Kaiser filter setup
• fir_filters_dask FIR filter functions operating on dask arrays
• iir_filters_numpy IIR filter functions operating on whole numpy arrays, classes to define filters and initial condition handling
• iir_filters_dask IIR filter functions operating on dask arrays

Changes to instrument:

• Replace AA filters with FIR filters from new modules. This still operates on whole numpy arrays as input and output, but internally uses dask-based filters, with a hard-coded chunk size.
• This "numpy-fication" of the dask functions is a temporary measure. Once the other parts are daskified, the AA filtering can use the dask filter directly. This will only require to change one line where the filter function is constructed.
• Moved setup of kaiser filter to new modules, made config parameter logic more strict, and temporarily diasallowed custom filter functions.
• Removed dummy MOSA parameter from filter functions since this has nothing to do with filtering. Added lambdas with the dummy where needed.
• Moved downsample filter definition out of AA filter setup method, and removed dummy parameter similarly as for AA filters.