Change the Rake task to one that uses namespaces as follows (previous task
names can also be used for compatibility).

| Previous Task  |    New Task    |
|----------------|----------------|
| api_doc        | doc:api        |
| capi_doc       | doc:capi       |
| clean_doc      | doc:clean      |
| clean_api_doc  | doc:clean:api  |
| clean_capi_doc | doc:clean:capi |
| view_api       | doc:view:api   |
| view_capi      | doc:view:capi  |
| gitlab_config  | gitlab:config  |
| gitlab_dockers | gitlab:dockers |