Added creation of tree data structure to DescendantsCrawler
Merge branch 'feature/EventDesign' of github.com:OpenDataSpace/CmisSync into feature/EventDesign
Added generic ObjectTree implementation for IObjectTree

Added also a ToList() method for IObjectTree to create a list containing all
items of the whole tree in a list.
Merge branch 'feature/EventDesign' of github.com:OpenDataSpace/CmisSync into feature/EventDesign