SegWit: TX ID over Essence only

[karimodm]

With the introduction of MultiAddresses, the TX ID becomes mallable.

"SegWit" would solve this problem, but we need think about how we handle multiple invalid and at the same time valid Transactions with the same TX ID then.

Additionally we should include the creation slot index in the TX ID, this way the created outputs would contain the creation slot index in their ID as well, which simplifies the mana calculations for clients, because the metadata of the output is not needed.