show schema config collapsed by default

This saves space on large schemas and makes it easier to focus at a
certain task.

We keep the new element expanded.

PHP code sniffer autofixes

load new config when changing the type in editor #74

fixed jsoneditor with renamed form element

better styling for disabled fields

added JSON editor

This makes editing the configuration for fields nicer. Types have to
define a complete (possibly empty) default structure and the editor
allows to edit it then.