Blind-signing flow changes

[apaillier-ledger]

Description

• hides the amount, which is usually 0 for smart-contract interactions which could give the user a false sense of safety
• shows a transaction hash (keccak-256 of the RLP)

Changes include

• Bugfix (non-breaking change that solves an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)
• Tests
• Documentation
• Other (for changes that might not fit in any category)

[0x398]

Please don't hide non zero amounts! It is usually zero, but I want to know when it is not. This way you hiding when some rogue smart contact want to steal ETH!