Add a few revert tests

[chris124567]

• Handle balance updates similar how to walletd does in AddSiacoinElements/RemoveSiacoinElements by calling ForEachSiacoinElement, separating outputs into slices of spent and new outputs, then processing from there. This fixed a few issues that occurred with reverts and ephemeral outputs.
• Fix bug which caused the genesis block to not be applied to the Explorer.
• Fix bug which caused foreign key constraints to not be enforced.
• Add tests similar to the apply block tests (TestRevertSendTransactions, TestRevertBalance) except that they revert some of the blocks and check that the state is correct afterwards.