Follow up for #1953404: Add config schema to field and instance config entities
Problem/motivation
#1866610: Introduce Kwalify-inspired schema format for configuration introduced the idea of config schema. The changelog leads to (hopefully extensive) documentation on the format at http://drupal.org/node/1905070. As a part of schema addition to field module(#1953404: Add config schema to field and instance config entities), found that we have to provide schema for field types, field widgets and field storage.
Proposed solution
Create a configuration schema for field types, field widget and field storage (if applicable) defined in image module.
Schema in place
field.image.settings
Note: Part of main field schema patch at #1953404: Add config schema to field and instance config entities
Schema not yet in place
field.image.instance_settings
field.image.value
field_widget.image_image.settings