Introduce the Image Caption plugin for Drupal.
Added the toolbar button.
Made the theme available by default.
Toggle the caption visibility on double-click.
Added "nocaption" check on downcasting.
Added the example "tips".
Data-widget attributes are not needed any more in templates.
Transform inline captioned image to block one.
Updated hint.
First, simple version of widget transformations.
Allow passing startup data object to initOn.
Always set data-widget attribute on widget's element.
Synchronize upcast and transformations on data.
Cleanup and comments.