Document TableCollection.load & update TableCollection.dump

[gregorgorjanc]

TreeSequence load method has doc at https://tskit.dev/tskit/docs/latest/python-api.html#tskit.load, but there is no corresponding doc for TableCollection load method.

I can see the method implementation at

tskit/python/tskit/tables.py

Line 3463 in dc394d7

def load(cls, file_or_path, *, skip_tables=False, skip_reference_sequence=False):

@hyanwong says: "Ah, yes, we should probably document this, as the reverse, https://tskit.dev/tskit/docs/latest/python-api.html#tskit.TableCollection.dump is indeed documented (although that needs updating too)"

[jeromekelleher]

Agreed this should be documented. A key use is for loading old tree sequence files that may not meet the sorting requirements post 1.0