Implement Query methods.

This patch implements eq, neq, lt, lte, gt, gte, and and or methods.
Implement Schema constructor.
Implement ScriptableDocument constructor.
Implement ScriptableDocument.objectID.

The oid is read only property that contains Object ID of document. If
it's not saved document, it contains empty string.
Implement ScriptableCollection.insert and ScriptableCollection.find method.
Implement ScriptableCollection.findOne().
Add getter of ScriptableDocument.