You can put the settings into a contracts.props file (or whatever you want to call it) and then import that file in all your projects.
You probably want to then delete the <CodeContractXXX>...</CodeContractXXX> settings in the project files.
Note that if you do this, you cannot change the settings from your project properties any longer. If you do, it will write them back into the project file and not into the shared imported file. That's just how properties work in VS project files.