…hing function

…gle matching function"

This reverts commit c798555.

Allow not providing signatures_catalog

To consistently use indices_associated_sigs.

Do not sort signatures. So that the returned signatures are the same as signatures, if signatures is complete, i.e., contains all connected signatures.

Now matching will always be performed with SparseNNLS with indices_associated_sigs set to None.

Then in the final W_s, we check what signatures are there, and add missing connected signatures if there are.

This is a better approach, because if we simply use indices_associated_sigs in SparseNNLS, then after _get_W_s() and _clear_W_s(), we may still lose connected signatures.