Move namespace from query param to path part

Per the accepted namespaces design, this PR modifies the URL patterns as follows:

| Action | HTTP Verb | Path | Description |
| ---- | ---- | ---- | ---- |
| CREATE | POST | /api/{version}/ns/{ns}/{resourceType}/ | Create instance of {resourceType} in namespace {ns} |
| GET | GET | /api/{version}/ns/{ns}/{resourceType}/{name} | Get instance of {resourceType} in namespace {ns} with {name} |
| UPDATE | PUT | /api/{version}/ns/{ns}/{resourceType}/{name} | Update instance of {resourceType} in namespace {ns} with {name} |
| DELETE | DELETE | /api/{version}/ns/{ns}/{resourceType}/{name} | Delete instance of {resourceType} in namespace {ns} with {name} |
| LIST | GET | /api/{version}/ns/{ns}/{resourceType} | List instances of {resourceType} in namespace {ns} |
| WATCH | GET | /api/{version}/watch/ns/{ns}/{resourceType} | Watch for changes to a {resourceType} in namespace {ns} |

The typical actor for the following requests are the k8s service or k8s admin as enforced by k8s Policy.

| Action | HTTP Verb | Path | Description |
| ---- | ---- | ---- | ---- |
| WATCH | GET | /api/{version}/watch/{resourceType} | Watch for changes to a {resourceType} across all namespaces |
| LIST | GET | /api/{version}/list/{resourceType} | List instances of {resourceType} across all namespaces |

The legacy API patterns for k8s are an alias to interacting with the *default* namespace as follows.

| Action | HTTP Verb | Path | Description |
| ---- | ---- | ---- | ---- |
| CREATE | POST | /api/{version}/{resourceType}/ | Create instance of {resourceType} in namespace *default* |
| GET | GET | /api/{version}/{resourceType}/{name} | Get instance of {resourceType} in namespace *default* |
| UPDATE | PUT | /api/{version}/{resourceType}/{name} | Update instance of {resourceType} in namespace *default* |
| DELETE | DELETE | /api/{version}/{resourceType}/{name} | Delete instance of {resourceType} in namespace *default* |

I was confused when porting this on how proxy.go actually worked, so at least my learning it was not for naught.