Add Object::objects message

For functions accepting object or non-empty list of objects.
Add tests of list arg of WithOrdinaryObjectSet
Implement list argument of WithOrdinaryObjectSet

It now accepts object or non-empty list of objects as first argument.
Modify tests of UpValues set in WithOrdinaryObjectSet
Fix restoring of UpValues in WithOrdinaryObjectSet
Add tests of WithOrdinaryObjectSet with flow control
Implement WithOrdinaryObjectSet flow control safeguards
Merge pull request #9 from jkuczm/with_ordinary_object_set

Enhance WithOrdinaryObjectSet