found a filter method on Graph
Introduced the SlicingGraph class
used implicit conversion method, although it is not used implicitly ...
first stupid version of slice. Might actually be conceptually close to what it might be like in the end
added test for edges. Put on pending, because I'll have to do some refactoring first
refactored classification of edges to constants
edges get considered for slices
checking for correct slice type on edges
refactored identification of nodes for slice
refactored identification of slice nodes for edges
refactored identification of edge projection into slices

As a side effect this fixed the warning, which would have causes problems with future tests
added comments, might need some further refactoring to make those superfluous
started building a slice finder partial function for identifying the slice node for a given node
slice finder now works properly with ParentAwareNode s
slice finder now considers containers
used SliceNodeFinder for finding slices. Fixed one glitch along the way