Merge taxonomies

[ospitia]

we have different options:

• instantiate all taxonomies and search simultaneously for parents and children of a shared initial node (query)
• leave the concept search as it is and merge the different related concepts from the different taxonomy instances

the advantage of the second is that we could have still the taxonomies separately, and an additional one called merged, the first option could be the same but it slows down the concept search because it's just adding more operations (but could be the best option in case we want to use only one taxonomy)

[ospitia]

merging concepts from different taxonomies could result in redundant concepts. We could use those redundancies to score the concepts and prioritize for displaying less crowded maps.