support optional leading slash in fully qualified names

[rabbah]

the leading slash in a fully qualified name is optional but appears to break the library here if it's not specified.

for reference, see: apache/openwhisk#2328

[jthomas]

The client library currently supports the following resource identifiers.

- resource_name
- package/resource_name
- /namespace/resource_name
- /namespace/package/resource_name

If we want to support a missing forward-slash for fully qualified names, how does the API differentiate between package/action and namespace/action.

Does it only support that the missing forward slash for actions within packages?

[rabbah]

This is the backend change that was implemented for reference in the cli https://github.com/apache/incubator-openwhisk/pull/2424/files

Three parts: unambiguous hence can drop leading slash.