1. data_dir is now a global setting in teleport.yaml (instead of being
inside of "storage" sub-section)
2. changing data_dir in one place causes all of teleport to use it,
not just bolt backends.
3. moving auth server to listen on non-default ports properly adjusts
the global auth_servers setting
4. `tctl` now accepts -c flag just like Teleport, so you can pass
`teleprot.yaml` to it.
Fixes#432Fixes#431Fixes#430
