fix(core): do not wait in case state was already reached

feat(core): avoid deadlock in contractor

fix(core): register contract after first state was executed

Merge pull request #55 from Rutherther/feat/contracts

Add contract system

feat(core): add default states and no errors enum

feat(core): add contract builder

feat(game): add timeouts to contracts

feat(core): add contract builder outline

feat(core): add basics of a contract system