Add function to cut the lowest element from a subtree
Add function for isolation of root node
Fixup documentation of isolate_root_node
Rename function cut_lowest to isolate_lowest
Fixup documentation of isolate_lowest
Extend internal documentation in isolate_root_node
Fixup: Rename function isolate_lowest to isolate_leftmost
Merge pull request #96 from neithernut/add-avl_internal-advl_del_prequisites

Add avl internal avl del prequisites