Cashout entire balance through bity.com

[TimDaub]

Scope

• Try cashing out all your ETH through bity.com
• You'll get the error insufficient funds for gas * price + value
• We believe that the user gets this error as there's not enough ETH in the account anymore to pay the gas cost for the actual transaction (or vice versa)

Deliverables

• Allow the user to cash out their entire balance using bity.com
• (Optional) Add a "max" button to bity.com dialogue "Amount"

Roles

bounty gardener: @TimDaub / 10%
bounty worker: name / 75%
bounty reviewer: name / 15%

[MaxStalker]

I suggest to resolve this one after #171 since "cash all/max" can be a part of 3 use cases:

• user wants to cashout all ETH and that value is below his annual cashout limit on bity.com or will not overflow it
• user wants to cashout MAXIMUM possible value without exceeding annual cashout limit
• user wants to cashout all ETH and he dosn't care about limits, since he filled all the necessary KYC information

In 2 of those we need to know exact value on how much is left and that what #171 shoul be able to provide