Display field definition settings

Related to: https://jira.ez.no/browse/EZP-20385

This patch provides the `ez_render_fielddefinition_settings` twig function. As its name suggests, it allows to display the field settings (and default value) of field definition depending on the field type.
Prior to this, this pull request also optimizes the `ez_render_field` twig function so that it does not search for the field block again and again.