[WIP] added has_any_tag and has_all_tags core filters to Theme API

Continuation of #1539 pull request (has_tag (single tag) )

* Added has_all_tags (AND) helper to core Helpers.
* Added has_any_tag (OR) helper to core Helpers.
* Added unit tests to check works as expected.

This patch adds functionality to support the following use cases:

* has_all_tags:

 ```html
        <section class="post-excerpt">
          {{#has_all_tags "summer of code" "snippet"}}
                <p class="code-snippet">{{content}}</p>
          {{ else }}
            <p>{{excerpt}}&hellip;</p>
          {{/has_all_tags}}
        </section>
```

* has_any_tag

 ```html
        <section class="post-excerpt">
          {{#has_any_tag "snippet" "code" "programming" }}
                <p class="code-snippet">{{content}}</p>
          {{ else }}
            <p>{{excerpt}}&hellip;</p>
          {{/has_any_tag}}
        </section>
```

This could be pretty useful to filter post types using tags.