Issue #1938390 by andypost, disasm, jibran, dawehner, ygerasimov, pfrenssen: Convert contact_site_page and contact_person_page to a new-style Controller.

Issue #2095121 by clemens.tolboom, jibran: Ensure every path in routing.yml files has a leading slash.

Issue #2089635 by tim.plunkett, disasm, larowlan: Convert non-test non-form page callbacks to routes and controllers.

Issue #1834002 by Gábor Hojtsy: Fixed Delete operations are all over the place. Remove tabs, provide title in routing.

Issue #2051097 by dawehner, Manuel Garcia, tlattimore, neclimdul: Change 'pattern' to 'path' in *.routing.yml files.

Issue #1981368 by tim.plunkett, Crell, webchick: Convert all routes to 'module_name().foo_bar()' naming convention.

Issue #2008356 by dawehner, tim.plunkett: Provide a _entity_list() route default to replace Controller\EntityListController and mimic _entity_form().

Issue #1856556 by Berdir, andypost, das-peter: Convert user contact form into a contact category/bundle.

Issue #1938386 by andypost, mkadin, tim.plunkett: Convert contact_category_()* pages to a new-style Controller.

Issue #1946366 by kim.pepper: Convert confirm_form() in contact.admin.inc to the new form interface.