Network Admin compatibility

[boonebgorges]

Currently, it's not possible to use the UIs when BP is network activated. This is primarily because the links point toward CPT screens, but CPT screens are mostly unavailable in the Network Admin.

Two possible ways forward:

(1) Always show the Types UIs in the root blog Dashboard, even when BP is network activated. Pros: this code is easy to write. Cons: Can no longer nest under the Groups top-level menu item; causes the administration experience to be fractured
(2) Show the Types UI in the Network Admin, but don't use the CPT interfaces. Cons: This will take a bunch of work.

I think (2) is the right answer, for reasons I'll spell out a bit in separate tickets.