Projects should not be able to vote

[ ] A mapping between address and bool should be introduced for disallowing projects to vote
[ ] This mapping should be synced with the project addition \ removal methods
[ ] A branch out of the completed pull request should be introduced with a temporary access controlled method should be introduced to sync the current projects to the mapping
[ ] Upon voting, the mapping should be consulted to check whether the voter is a member project, and if so the voting should be reverted
[ ] A test checking this behavior should be introduced

BreadchainCoop / breadchain