* Fix F-3: Explicit Variable Return audit report
* Reuse onlySecurityCouncil modifier and update its revert message
* Fix F-5: modifier Optimization audit report
* Fix F-7: Input Sanity Check audit report
* Add audit report
* Further gas optimise getting a checkpoint function by up to 100 gas
* Fix F-6: return Statement Optimization audit report
* Wrap logic in unchecked block to save 24 gas
in getVotes and getQuadraticVotes each
* Move audit doc into a dedicated folder
cfbb9c6f6c