Keep a track of the dividend distributed

[rya-sge]

To know the remaining balance after distribution, it could be relevant to keep a track of the distributed sum for a specific dividend.

Example
mapping(uint256 => uint256) public segregatedDividendClaimed;

And rename segregatedDividend in segregatedDividendDeposit

When a dividend is deposit:
segregatedDividendClaimed += value

When a dividend is claimed
segregatedDividendClaimed -= value

After the end of the distribution, it is easier for the operator to withdraw the remaining dividends after distribution