Claims now use wb.SnakList instead of wb.Snak[] for their qualifiers

Adjusted tests and solved some overdue TODO there along the way.

Change-Id: I2e2688c23c05bcf3bf1d61cd4b8f02675485dd3e
implemented wb.Claim.equals

Change-Id: If07ea5ff7bc2e6ccc1a112ed4bc398b42a10466b