Merge: nitweb: auto link entitites found in `span code`

Merge: nitweb: auto link entitites found in `span code`

This PR introduces a stub feature for nitweb: autolinking entities from `span` code.

Each time nitweb renders a Markdown comment it evaluates the content of each inline `code` tag and tries to match it with the model index. If the content of the `code` tag matches a package, module, class or property, the `code` content is wrapped in a link to that entity.

Examples:

* `Object`: will be rendered as `<a href='/doc/core::Object'>Object</a>`
* `nullable Object`: will be rendered as `<a href='/doc/core::Object'>nullable Object</a>`
* `is_same_instance`: will be rendered as `<a href='/doc/core::Object::is_same_instance'>is_same_instance</a>`.

The name matching algorithm is the same as the one used to resolve short links like `[Object]` or complex directives like `[graph: core]`.

Demo: http://nitweb.moz-code.org

The documentation from the `core` package benefits from the new feature: http://nitweb.moz-code.org/doc/core

Pull-Request: #2353