Make HierarchyTree class copy and move constructible, and copy and move assignable

[beingkartik]

The HierarchyTree class is currently not copyable/movable currently. While the operations succeed, they cause issues due to memory managed using raw pointers.

For example, currently on copying a HierarchyTree, the copied-from and copied-to both have pointers to the same memory, and both attempt to delete the same memory, which is undefined behaviour.

As per the c++ standard guidelines, specifically the rule-of-three and rule-of-five, we should implement the copy+move constructors and assignment operators.

I will be happy to provide a pull request if the team is willing to consider this. This would involve recursively copying the tree for copy and cleaning transferring ownership for move.

wdyt?

[jcarpent]

Very nice initiative @beingkartik.
We can assist you in this process. We inherit the raw pointers from the seminal FCL library that definitely needs to be updated.
Thanks in advance for your contribution.