Deleted the 2D system normalization methods and the sqrt_svals feature.

This was done because it is very unlikely that the
normalization are useful in practice but they cause the code
(in particular the implementation of normalizeAxis) to be
more complicated.
Added an additional check to the normalizeAxis test.

Specifically, I added a check that absorbing the
normalizer into the original data obtains the normalized
data.
Fully documented NDArrayData!!!
Documented carcassonne.data.cost_tracker.
Simplified computeCompressor by removing the unused normalize feature.
Now old_dimension in computeCompressor* is automatically inferred from the shape
Moved computeNormalizerAndInverse to carcassonne.test_utils

as this is the only place where it is used.
Deleted unused function formAbsorber.
Deleted unused function formContractor (and prependContractor).
Now dimension_of_krylov_space defaults to 3 instead of None.

This slightly simplifies the implementation and
explanation of the relaxOver function in utils.
Documented carcassonne.utils!
Documented carcassonne.compression.
Deleted the unused (and broken) alternating dimensions bandwidth increase policy
Documented carcassonne.policies.
Fixed stupid implementation of id argument in OneSiteTensor.
Documenting carcassonne.sparse in progress...
Wrote utility script grep-for.sh