Compares the two given social commitments. The comparison is is designed to
give the commitments an ordering. The fields of the two commitments are
compared in the following order, with the first difference determining the
ordering of the two commitments:
- The social commitments are sorted by their priorities (with the
highest priority first).
- Unfulfilled social commitments come before fulfilled commitments.
- Fulfilled social commitments are sorted by their fulfilment time.
- The social commitments are sorted by their actions.
- The social commitments are sorted by their creation time.
- The social commitments are sorted by their debtors.
- The social commitments are sorted by their creditors.
If the two social commitments are equal in all of the above comparisons,
they are equal.