Issue #2350837 by dawehner, Berdir, larowlan, Wim Leers: Convert most usages of EntityInterface::getSystemPath() to use routes

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