Commit #10

JobsManager:
  + added remove(String)
  + added get(String)
  + added exists(String)
Tree:
  + added exists(String)
  + added find(String)
  + added remove(String)
Node:
  + added find(String)
  + added remove(String)
  + added getParent()
  + added setParent(Node<T>)