Don't create a merged property if the composition is on object level about php-json-schema-model-generator

[wol-soft]

The current process of resolving a composition looks like:

1. addComposedValueValidator gets a property which has a composition keyword
2. A new dummy-property is initialized to represent the composition (without knowledge about the provided property)
   1. The dummy-property is generated via the ComposedValueProcessorFactory
   2. For each composition element another nested dummy-property is generated (this time via the PropertyProcessorFactory, nested inside a CompositionPropertyDecorator)
   3. Out of all nested dummy-properties a merged-property will be generated which will be used as property type for the property holding the composition (the merged property contains all nested properties of each composition element, several TODOs waiting at that point to not create a merged property if none or only one composition element with nested properties is provided)
3. All validators of the first dummy-property will be transferred to the provided property to make sure the property is validated against the composition

To make it possible to determine inside the dummy-property whether it's a composition on object or on property-level the information about the current level has to be provided to the dummy-property via the ComposedValueProcessorFactory.

If the information is available, only create a merged property if the composition is located on object-level