An "includes" flag to facilitate some structure uses

[jacomyal]

I would like to declare custom structures, such as the data has to include some typed values associated to specified keys, but it can contain some other keys.

Here is an example of how I'd like to use that:

// Structure declaration:
domino.struct.add({
  id: 'myStruct',
  includes: true, // indicates that other keys can be used
  struct: {
    myKey: 'string'
  }
});

// Some tests:
domino.struct.check('myStruct', {
  myKey: 'myValue',
  anotherKey: {
    containing: 'anything'
  }
}); // would return true
domino.struct.check('myStruct', {
  myKey: 42
}); // would return false