Merge Menu Environments and Items

[rabrowne85]

I'm not sure why we have these two separate. The nested set type allows for these to be merged.

@frankpde: what do you think?

[frankpde]

We can drop environment and environment_id. Identifier would be the L1 node for retrieval.

Identifier column should hold the full route name.

We can also consider using the route actions on top.