Feature/sorta

1. Split ontology related classes into two modules. The reason is that there was a cyclic reference, molgenis-ontology ----> molgenis-data-mysql ----> molgenis-data-semanticsearch ----> molgenis-ontology
    - molgenis-ontology-core only contains classes related to ontology repository as well as ontologyService
    - molgenis-ontology contains the ontology related tools, such as SORTA and ontologyTree

2. According to some of the feedback received from developers, some of the texts were confusing, so updated some of the text for clarification purpose

3. Added delete function to delete existing matching task
Methods of this class should be synchronized as it can be used by multiple threads