EZP-21107: refactored REST input as sf 2 services

Jira issue: http://jira.ez.no/browse/EZP-21107

Adds two service tags: `ezpublish_rest.input.parser` and `ezpublish_rest.input.handler`.

Examples:

```yaml
services:
    # input handler
    ezpublish_rest.input.handler.json:
        class: %ezpublish_rest.input.handler.json.class%
        tags:
            - { name: ezpublish_rest.input.handler, format: json }
    # input parser
    ezpublish_rest.input.parser.ContentUpdate:
        parent: ezpublish_rest.input.parser
        class: %ezpublish_rest.input.parser.ContentUpdate.class%
        tags:
            - { name: ezpublish_rest.input.parser, contentType: application/vnd.ez.api.ContentUpdate }
```