Likelihood -> Likelihood energy
Prior -> Prior energy

This resolves deprecation warnings in numpy>=1.2 .

This was achieved by exploiting the diagonality of the Fisher metric.
In cases this is not true one needs more samples to increase sensitivity.
Tested that a factor of 2 only in the inverse covariance can now be detected.

Since `noramlized_ampliudes` is not a property anymore, name it more
actively as to highlight the need for it to be called as a function.

The zero-mode must not be known for constructing amplitudes. Only when
finalizing the model, the zero-mode needs to be specified. Honor this by
pulling all parameters relating to the zero-mode to the `finalize`
method.

Move `moment_slice_to_average` outside of `CorrelatedFieldMaker` as it
does not depend on nor require the inherent structure of the class.