refactoring to make storage scheme simpler (removed one of the trees)
forgot to add basic tests file
minor fix
added some basic functionality
added missing files (from last commit)
minor
added some safety precautions
added iterators to nodes and edges
removed unneeded property
major refactoring  - make API more consistent, and use integer keys that are generated by the system
reimplemented add edge and iterate on edges now work.
refactoring/reimplementation WIP. uncommented relevant unit tests
refactoring almost complete. what remains is to fix the last failing unit test and add some more tests to verify special/original use cases
some refactorings, unit tests work
add two more tests
deleted unneeded properties
Merge branch 'master' of https://github.com/myarichuk/Voron.Graph

Conflicts:
	Voron.Graph.Tests/BasicTests.cs
Merge branch 'master' of https://github.com/myarichuk/Voron.Graph.git
refactored id generation (introduced conventions to GraphEnvironment, changed Id generation to HiLo algorithm)
added missing file