Incoming/Outgoing SwapCoins incorrectly use Hash256

Not a huge deal but I just noticed the IncomingSwapCoin and OutgoingSwapCoin types use the type Hash256 for the hash preimage, but that is conceptually wrong, because the preimage isn't a hashvalue.

teleport-transactions/src/wallet_sync.rs

Line 109 in fded48e

pub hash_preimage: Option<Hash256>,

teleport-transactions/src/wallet_sync.rs

Line 123 in fded48e

pub hash_preimage: Option<Hash256>,

Again I emphasize it's not a huge deal, just conceptually wrong. Maybe it could be replaced with a type Preimage which could be created if it doesnt already exist, or just revert back to [u8; 32].