Adding a removeAllChildren method

- Remove all children, removing the name references and index
- This method calls removeFromParent on the children so it also removes the child's DOM.
Adding a removeChildren method

- Remove all children, removing the name references and index
- This method calls removeFromParent on the children so it leaves it up to the child to remove itself in whatever way it needs to. IE: DataView's also remove their DOM.
Merge pull request #4 from taskrabbit/container-removes-all-children

Adding a removeChildren method