This reverts commit 8b82159ee0.

This confirms that in addition to the recently added support for dotted
subdomains that subdomains that are not dotted are supported.  From
RFC1034 Section 3.5 this would be a <subdomain> that contains a single
<label> without <subdomain> recurring.

The is not a zone between delegated.subzone.unit.tests. and unit.tests.,
however we get a delegated subzone error.  This modifies the tests to
succeed with the added record, however the tests fail as it incorrectly
throws the managed subzone error.

Change the name of delegated.subzone, and the tests will pass cleanly.

This will result in less churn in tests for root NS support and allow us
to enable/disable things easily as needed.

support them

aliases zones in the target zone configuration

This reverts commit b926d78c5c.

This commit adds support for zones aliases. This allows to define one or
multiple zone as aliases of an existing zone without using workarounds
like simlinks and miltiple "zones" entries in the configuration file.

An alias zone is share all of its content with it parent zone, only the
name of the zone is different.

```
zones:
  example.com.:
    aliases:
      - example.net.
      - example.org.
    sources:
      - in
    targets:
      - out
```

Known issues:
- No documentation,
- Only the `octodns-sync` and `octodns-validate` commands supports
aliases zones at this time,

I added a loop in the manager init function which convert all alias
zone to "real" ones during config validation, however I'm not sure
this is the right approach. Comments welcome.

That's all Dyn supports and it's cleaner to match it than to scale dyn since
we'd lose precision we can't get back during populate.

Signed-off-by: Christian Funkhouser <cfunkhouser@heroku.com>

The SplitYamlProvider itself now requires a directory matching the
zone name under its directory to contain all YAML files. This doesn't
actually change the intended usage at all, just how the configuration
file is laid out.

Signed-off-by: Christian Funkhouser <cfunkhouser@heroku.com>

Signed-off-by: Christian Funkhouser <cfunkhouser@heroku.com>

Refactors the provider class lookup and kwarg processing so that it can be
reused for plan_output.