Create AVLTree skeleton
fix compilation errors and implement single rotation right
add single rotation right unit test
Implement single rotation right
single rotation left unit test
implement insert and add interfrace for double rotations
implement double rotation right
double rotation right unit test
implement double rotation left
unit tests for double rotation left
Update node height in single rotations
test height in single rotation right
check height in single rotation left
check height in double rotation right
chech height in double rotation left
implement node remove
fix btree clear
add btree clear unittest
btree height test
btree find unit tests