Syntax for referring to item versions

Some work is already done to versioned actions, but it's not expose in CLI and other items like rules, triggers, feeds will need to be doc.

From @vinodmut :
All items are versioned using semantic versioning. We need a way to refer to particular versions of items.

This is needed both in the CLI and API.

A proposal for the syntax that continues to use ':' delimiters:

Fully qualified name with version would look like:

```
namespace:name:version
```

So examples include:

```
bob@example.com:myaction:0.1.0
bob@example.com:myaction:0.1.*
bob@example.com:myaction:>=1.2.3
bob@example.com:myaction:~1.2.3
bob@example.com:myaction // implies latest version
```

The versioning syntax is based on the semantic versioning as supported by npm: https://github.com/npm/node-semver

Since we allow arbitrarily nested namespaces, and both namespaces and versions are optional, we can avoid ambiguities by requiring that namespaces and item names start with [a-zA-Z]. Versions would start with [0-9~><=^].

Start by reviewing the existing work on versioned actions and tracing how item names are handled in the CLI and API. Compare the proposed namespace:name:version forms with rules, triggers, and feeds; done means a decided syntax and consistent support for the documented version selectors.

Written by the indexing model from the issue text.