Refactor the terminology contributors

[f-gate]

Instead of using ContributionsFor<T> for we have a VoteWeight and change the terminology from contributors to voters.
This would take out the magic in the proposals pallet and make it more readable.

Currently we hack our way through for Grants and give each approver equal contribution, while contribution should be 0, VoteWeight should be equal. This is true to the actual state of things. as opposed to a hack to mimic the state of things.