enrich association-model to specific child-topics when building up new TopicModels

[Malte]

Potential associations (to Child-Topics) should be already addressable (available for further operations, like e.g. setting a Property) when one has just build up a TopicModel?() of a specific type. The wikidata case needs an extended TopicModel? to store (potential) Properties for involved Topics and their Associations. But this is not just for properties, think about setting up child topics on a specific association to a specific child-topic while building up a complex TopicModel? of a specific type (in advance).

Background:
The wikidata case needs an ordinal number on the edge to composed wikidata-search-entities to maintain the oder of wikidata-search-entity-buckets across all potential search results.

[jri]

This is now addressed for DM 4.6 in the course of #341 (see section "Protocol" in the ticket description).

[jri]

Note: the particular child topic aspect is addressed separately in #785