[BSTree.cs] initial commit
[BSTree.cs] realize base interface
[Extensions.cs] add the extension check to null
[BSTree.cs] add bstree validation method
[BSTree.cs] add find method
[BSTree.cs] add insert method
[BSTree.cs] add remove method
Revert "[BSTree.cs] add remove method"

This reverts commit aee4795466ab1476a276c76eb5360f702a222961.
[BSTree.cs] add remove method
[BSTree.cs] refactoring
[BSTree.cs] fix tests
[BSTree.cs] add traverse methods
Merge branch 'feat-BSTree-class'
Merge branch 'master' of https://github.com/demon1234432/my-Humble-Repository-of-Useful-Code