refactor: include version in the wallet_tx_history table to avoid a JOIN on tx_history query

[andreabadesso]

I know that we already have this information on another table and searching for it makes sense, but why not add the version on the wallet_tx_history table?

This would involve more work to update, but the update of old data can be done in the migration and it would be faster to get the tx history (a query that will be made very frequently)

Originally posted by @r4mmer in HathorNetwork/hathor-wallet-service#199 (review)