[1.0.0-beta1] Allow icon picker selection

Partially done:
Field UI: ok
CKEditor: Dialog in Dialog is more complicated than expected... needs investigation.
UI Patterns: not sure if we can select somewhere or need a Plugin for each, need discussion with @pdureau.

As discussed with @pdureau, UI Patterns need another source that can be provided later or by another module.
CKEditor is complex and need it's own issue.

Automatically closed - issue fixed for 2 weeks with no activity.