Issue #2407195 by Wim Leers, Fabianx, joelpittet, lauriii, Crell: Move attachment processing to services and per-type response subclasses

Issue #2339491 by corbacho, dawehner, larowlan, effulgentsia, webflo: Ajax requests on forms with files fail on IE 9

Issue #2250165 by neclimdul, cs_shadow, YesCT: Replace fake mocks with actual OpenDialogCommand stubs in AjaxCommandsTest

Issue #2361681 by Wim Leers: drupal_render(): invert second argument ($is_recursive_call -> $is_root_call) => more strict, better DX/TX.

Issue #697760 by sun: Replace getInfo() in tests with native phpDoc + annotations (following PHPUnit).

Issue #2171071 by jessebeach, dawehner, chakrapani, longwave, Gábor Hojtsy, xjm, Wim Leers: Rename drupal_add_library() to _drupal_add_library() and remove its uses.

Issue #2187483 by Cottser, agentrickard, dawehner, jessebeach: Toolbar subtree is broken | JsonResponse->callback now returns data in an Insert Command without any support in ajax.js to eval the callback in the client.

Somehow this broke PHPUnit, so rolling back for now.

This reverts commit 91b465bd.

Issue #2107199 by Wim Leers: Allow Close(Modal)DialogCommand to remove the dialog from the DOM, document how client-side dialogs can do that too.