Convert theme_image() to Twig

Task

Use Twig instead of PHPTemplate

Twig sandbox: http://drupal.org/sandbox/pixelmord/1750250

Remaining

• Replace all theme functions and templates with .html.twig equivalent templates
• Add new preprocess functions for the .html.twig equivalent templates
• Update all hook_theme definitions

Related

#1643894: theme('image')
#1885560: [meta] Convert everything in theme.inc to Twig