updates in PreservedFunctionalAttributes

- removed constraint that object should not be built by foreign key
  values
- adjusted tests
- expanded the search for owl:FunctionalProperty to whole set of view
  definitions
- replaced tabs with spaces
- surely some minor updates that I forgot
moved PreservedNotNullConstraint metric and tests to new structure
renaming of 'mapping' to 'view'
small fix fir DatasetMetadata metric

- added handling of the case, that no dataset prefix is set
just tab alignment changes on HttpUri metric
updates and fixes on LabeledResources metric and tests

- replaced model querying with explicit SPARQL queries
- removed rdf:comment consideration
- updated tests accordingly
fixes on metrics.properties