HTML cleaner plugin should have configurable service ID

The client-side HTML cleaning in CKEditor is configurable per field [1]. Currently, the service ID of the HTML cleaner plugin is hardcoded as "org.hippoecm.frontend.plugins.richtext.htmlcleaner.IHtmlCleanerService". As a result, there can only be one HTML cleaner service defined in the system.

When multiple fields use different client-side HTML cleaning settings, the server-side HTML cleaning should be kept in sync (e.g. when the client-side HTML cleaner no longer allows <strong> tags, they should also be removed by the server-side HTML cleaner).

The service ID of the HTML cleaner plugin should therefore be configurable, so there can be multiple instances that are used by different HTML fields and reflect the field-specific client-side HTML cleaning configuration.

[1] http://www.onehippo.org/library/concepts/document-types/html-fields/html-cleaning.html