Add sample-rate-cut and low-frequency options
This PR adds the option to restrict the sample rate of channels in a config file and set a common low frequency bound for all channels. This will be used to build config files for high frequency omega scans (flow=1000, remove slow channels, plot up to Nyquist) as such:
python clf-to-pyomega.py -o test-sample-rate-lowf.ini --nyquist --sample-rate-cut 4096 --low-frequency 1000 ../O3/L1-O3-standard.ini
The logic in place reproduces the original functionality if these arguments are not provided