Adds namespace support to the UI:
1. Namespace CRUD/management
2. Show Namespace in relevant areas (intentions, upstreams)
3. Main navigation bar improvements
4. Logic/integration to interact with a new `internal/acl/authorize` endpoint
* ui: Add ember steps:list command for listing available steps
1. Adds `command` addon to house the new command
2. Start to organize out the steps themselves, bring a bit more order to
things ready to dedupe and cleanup