Refurbish deposit validation to allow coinffeine-server to use it

**Description:** refurbish deposit validation to allow coinffeine-server to use it. This is the last PR before having the server module working again.
**Testing:** tests pass.
**Coverage:** 93% for DepositValidator.
That forced me to change all the checks related to keys order in the transaction script. A step forward anyway. See 40e66784c29394f5325c4bd07eb03b4e52a0962b