Fix __PROJECT_NAME__ replacing code

`&` is a special character for `sed` and this fixes the problem of having `__PROJECT_NAME__` in the final output when the project name contains an ampersand, this is not only a cosmetic issue but also leads to compilation errors:

    xcodebuild: error: The project 'A&B.xcodeproj' does not contain a target named 'A&B'.
    { [Error: /Users/lapo/projDir/platforms/ios/cordova/build: Command failed with exit code 65] code: 65 }
       [error] /Users/lapo/projDir/platforms/ios/cordova/build: Command failed with exit code 65