Moritz Huebner: Removed default parameters for sampling frequency and time duration in the waveform generator

Clean up the logic of fill_priors and close #58

Closes #58

See merge request Monash/tupak!36

If a label is given to setup_logger, the output is written to a file.

- Removes the 'bad_keys' part of the logic. I believe this was
  essentially adding the keys which where not given in the prior and
  that had no default prior, and then removing them at the end.
- Change the logging output slightly: now the only warning that is given
  is when no default prior is known. Other output at info level
- Add in what the waveform_generator knows about missing keys (useful
  for diagnosis
- Formatting of the docstring

Prior tests

See merge request Monash/tupak!35

Default prior bounds

See merge request Monash/tupak!34

Allow multiple prior draws

See merge request Monash/tupak!33

- Rename n_samples to size to fit with standard numpy conventions
- Fix check to handle multiple values

Functionally, this changes nothing, but it makes it clear that the
filled priors are the dictionary `priors`.

Previously, the dynesty kwarg for the number of live points was set to
be `npoints`, and so `npoints=10000` was passed to
`dynesty.NestedSampler`. This, however, is not the kwarg requried by
`NestedSampler`, but it instead should be `nlive`.  Unfortunately, this
error is silenced because the kwargs are just lost in dynesty.

- Fixes nlive kwarg
- Reduces default number from 10000 to 250 (as this was what was
  actually used before)
- Adds a verbose flag controlling the `run_nested` argument
  `print_progress`

Add minimal example and associated helper functions

See merge request Monash/tupak!32

- Adds an example showing the simplest number of steps to run PE on
  GW150914
- Adds a helper (rapper) function to quickly get the BBH likelihood
  instance

- Add ability to pass in parameters as either keys or latex labels
- Update truth to not overwrite the given kwarg, but preserve "plot
  injections by default" behaviour.
- Add function to convert a set of parameter_keys into the latex labels
  used by CC

- Set plot=False during tests
- Remove verbose=True from nestle calls