Improve logging

[MijnheerD]

The current logging (which consists of some print statements) is not easy to read and/or interpret.

I have a couple of suggestions for improvements that could help with this:

• First I would use the Python logging module. Even using the default implementation would be fine, allowing users to select what messages to see.
• It is not clear what frequency range the interpolator is using. The default is [30, 500] MHz but this can only be seen when digging through the source code. The logging output never mention this range, as can be seen in the image below showing the output of instantiating an interpolator object with almost all values kept to the default (but verbose=True of course):
  
• Having 196 prints while generating the interpolators floods the stdout completely. Using a progress bar would be optimal, but would require an additional dependency (something like tdqm for example). Another option would be to only log every x amount of creations. Or, using the Python logging module, these could be added to DEBUG or even a custom PROGRESS level which a user can easily filter out.

[acorstanje]

What is printed here is really debug info that I used when developing the first version...
We could choose to remove a lot of it (definitely the xx/196 ones) or make the steps more descriptive.
Using the standard logging would be good.