Issue #1364670 by mondrake, mrfelton, dinarcon, das-peter, zuuperman, er.pushpinderrana, cchanana, drupaldrop, fietserwin: ImageStyle::transformDimensions unable to deal with all effects

Issue #2420751 by Wim Leers, mondrake, attiks: ImageEffectBase::transformDimensions() should have a sane default implementation

Issue #2330899 by attiks, Jelle_S, fietserwin: Allow image effects to change the MIME type + extension, add a convert image effect.

Issue #2272481 by herom, ParisLiakos, tim.plunkett: Remove usages of watchdog() from forms, plugins and controllers.

Issue #1898420 by mondrake, joelpittet, InternetDevels, claudiu.cristea, c4rl, DamienMcKenna, Albert Volkman, shanethehat, thedavidmeister: Image.module - Convert theme_ functions to Twig.

Issue #2248151 by tim.plunkett, xjm, alexpott: Configurable plugins can not control instance-specific config dependencies.

Issue #2087231 by tim.plunkett, pwolanin: Add a PluginBase in the Core namespace with t() as a helper method.

Issue #2062573 by claudiu.cristea, tim.plunkett, Xano: Change notice: Add method defaultConfiguration() in ConfigurablePluginInterface.

Revert "Issue #2062573 by claudiu.cristea, tim.plunkett, Xano: Add method defaultConfiguration() in ConfigurablePluginInterface."

This reverts commit bf37effc.

Issue #2062573 by claudiu.cristea, tim.plunkett, Xano: Add method defaultConfiguration() in ConfigurablePluginInterface.