suggstion for ontology icons
2nd suggstion for ontology icons
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.
replace remove shoulda matchers with asserts

- since shoulda 2.0 some matchers have been
  [remove](http://robots.thoughtbot.com/post/47031676783/shoulda-matchers-2-0).
add tabs to logics#show view

The Logics show page is now somewhat more
analogue to 'the show page' of ontologies.
add tab-view for hom. DOs in logic.

Display a tab which will list all homogeneous
Distributed Ontologies which children belong to
the given logic.
fix active-tab display issue.
add test for logic-specific het. DO-fetch method.
add method to fetch logic-specific het. DOs

- add a method to fetch the logic-specific
  heterogeneous Distributed Ontologies
- Refactor duplicate code into own method (DRY)
- Use "speaking" constants instead of
  seemingly arbitrary strings.
add display of logic-specific het. DOs

This adds a new logics#show subview/partial for display of the
heterogeneous Distributed Ontologies which have at least one child
that uses the logic.