Issue #2665992 by alexpott, klausi, heykarthikwithu, xjm, tstoeckler: @file is not required for classes, interfaces and traits

Issue #2329795 by fietserwin, bzitzow, alexrayu, tstoeckler | illutek, dawehner: Fixed Make it possible to add information to theme info files during development.

Issue #2238217 by effulgentsia, neclimdul, martin107, tim.plunkett, cweagans, kim.pepper, xjm: Introduce a RouteMatch class.

Issue #1954892 by dawehner, David_Rothstein, tim.plunkett: Replace 'theme callback' and hook_custom_theme() with a clean theme negotiation system.

Revert "Issue #1954892 by dawehner, tim.plunkett, David_Rothstein, effulgentsia: Replace 'theme callback' and hook_custom_theme() with a clean theme negotiation system."

This reverts commit fc04601c.

Issue #1954892 by dawehner, tim.plunkett, David_Rothstein, effulgentsia: Replace 'theme callback' and hook_custom_theme() with a clean theme negotiation system.