Add Distribution Helpers

[sheharyarn]

Related to #15 and #17.

Add more mnesia wrapper methods to easily add new cluster nodes to the mnesia config and change schema, copy type, waiting for tables to get ready and more.

• [x] Connect Nodes
  • [x] Memento.add_nodes(nodes)
• [x] Schema wait
• [x] Schema copy
  • [x] Memento.Schema.set_storage_type(node, mode)
• [x] Table copy
  • [x] Memento.Table.create_copy(Jobs, node, mode)
  • [x] Memento.Table.delete_copy(Jobs, node)
  • [x] Memento.Table.move_copy(Jobs, from_node, to_node)
  • [x] Memento.Table.set_storage_type(Jobs, node, mode)