Adding Balanced tree graph and tests
Adding Wheel graph and refactoring other classic and named graphs

Refactoring:
Deleting bipartite, star and petersen digraph and associated tests
Adding house and houseX named graphs
Fixing bug in wheel graph and adding tests

Tests:
- Wheel0GraphTest
= Wheel5GraphTest
Fixing bug in HouseX graph and adding tests for them (house and houseX graphs)