activate graphs controller route for ontologies.
handle empty nodes and empty edges in graphs.
adjust graphs controller tests for empty results

- Test for return of valid response when calling
  graphs on logic/ontology without mappings/links
- Remove obsolete user portion (factory takes
  care of that).
add tests for hetereogeneity and homogeneity.
extract complex ontology-builder into factory

- also add missing user association to logic-factory.
add code for homogeneous distributed ontology

- add two methods to determine whether
  an ontology is heterogeneous or homogeneous.
add tests for homogeneous/heterogeneous query.
add minimal working versions for queries

- since they rely on ruby's select method,
  they are quite slow and will be optimized
  by an sql-query later.
add display of heterogeneous ontologies in logics.
replace minimal queries with sql-based queries.
determine heterogeneous children with sql.
add test for fetching DOs which belong to a logic

- It should be possible to fetch those homogeneous
  distributed ontologies which *belong* to a logic in
  the way that all child ontologies belong to that logic.
add passing code for logic specific DO fetching.
add display of logic specific DO count.
Merge issue190... into augmenting112... for tabs

Merge 'origin/issue190-optimize_ontology_title_bar' into augmenting112_ontology_link_graph
Add Tests for determining Mapping-Class as Symbol.
implement passing version of mapping-query.
add graph as own view for graphs#index action.
Merge issue190... into augmenting112 for pages

Merge remote-tracking branch 'origin/issue190-optimize_ontology_title_bar' into augmenting112_ontology_link_graph
adjust js code to work with graphs#index view.