feat: add direct sell support

[troggy]

Given:

• user with plasma tokens wants to fast exit them

Flow:

• user queries /deals endpoint to see if there is a market and liquidity for a given token
• if user decides to proceed, he transfers his tokens to market maker address on plasma. Address is provided by /deals endpoint as well
• user does POST /directSell with { txHash } payload. Market maker should check given tx and payout the user on the root network. Endpoint returns txHash of the payout
• (optionally, for sunDai) user waits for payout tx to mine and executes burnSender to get his DAI on the root network

Market maker performs the following checks on provided txHash:

• should be included in a block
• should not be payed out already
• should spend to market maker address
• market should exit for the color in tx
• balance for the token should be enough for payout

Payout rules:

• payout goes to the signer of the tx input
• payout amount is the value of the first output to market maker.

[TimDaub]

Just got this on the testnet market maker:

{"errorMessage":"timeout","errorType":"Error","stackTrace":["Timeout._onTimeout (/var/task/src/exitManager/index.js:10993:20)","ontimeout (timers.js:482:11)","tryOnTimeout (timers.js:317:5)","Timer.listOnTimeout (timers.js:277:5)"]}