Add ERC20 support to SplitPayment

[frangio]

SplitPayment allows a group of people to receive ether payments proportionally to their shares. The function claim extracts the correct amount of ether. We should add support to receive ERC20 token payments and for payees to claim them, probably through a claim(ERC20 token) function.

See #859 for a use case.

• 📈 This is a feature request.

[pw94]

Hey, I would like to code it. I have started to do it but I came accross two issues:

• Would the contract be used to maintain tokens and eth value simultaneously? If so, I should track totalReleased value (eth) and tokenTotalReleased separately as well as released values.
• Since to use token I need only balanceOf and transfer functions I can use sufficient ERC20Basic instead of ERC20 in claim function?

[frangio]

Awesome @pw94!

1. You should have a mapping (address => uint256) tokenTotalReleased for each token address, as well as mapping (address => mapping (address => uint256)) tokenReleased for each token address for each account.
2. Yes you could just use ERC20Basic.

[Aniket-Engg]

@frangio This would be great if you can review the PR so that current status of issue can be known.

[nventuro]

@Aniket-Engg much has changed since that PR was opened, so some updating will need to be done. I'll try to review it during these next couple days.

[frangio]

This is part of a bigger challenge we have of uniformly handling tokens and ether in several of our contracts. We don't have a good design for this yet. Related to #1099.

[frangio]

Fixed in #2858.