Removes line which saves the raw dynesty output to file

- Removes the old custom_source tutorial
- Adds comments to the create_your_own_source_model

This reverts commit f04ab987

Moritz Huebner: Added FFT/IFFT functionality to create strain data for both domains even if only one source model is given.

# Conflicts:
#	tupak/prior_files/comoving.txt

Adds the sampling frequency and duration as interferometer attributes

See merge request Monash/peyote!29

# Conflicts:
#   tutorials/GW150914.py

- This simplifies the way things are passed around
- Also fixes the spelling mistake of "interferometer" (my bad)