Issue #2167623 by danilenko_dn, sidharthap, Nitesh Sethia, krishnan.n, aitiba, alexpott, ashwinikumar, Barrett, damiankloip, deepakaryan1988, foxtrotcharlie, ianthomas_uk, neetu morwani, nonsie, piyuesh23, Sharique, sivaji, sushantpaste, swentel, vijaycs85, YesCT: Add test for all default configuration to ensure schema exists and is correct.

Issue #1862202 by plach, Berdir, katbailey, ParisLiakos, alexpott, chx, sun, larowlan, Gábor Hojtsy, cosmicdreams, vijaycs85, YesCT, penyaskito, andypost, Albert Volkman, joelpitett: Objectify the language system.

Issue #2133325 by mtift, alexpott, sun: Create a site UUID on install and only allow config sync between sites with the same UUID.

Issue #2130811 by alexpott, Gábor Hojtsy, vijaycs85, sun, Wim Leers: Use config schema in saving and validating configuration form to ensure data is consistent and correct.

Issue #2098089 by penyaskito, Schnitzel, tim.plunkett, YesCT, EllaTheHarpy, Gábor Hojtsy: Fixed Date formats cannot be translated (the core UIs are useless).

Issue #2084339 by alexpott: Fixed The configuration value system.maintenance.enabled should be moved to the state system.

Issue #1934712 by dlu, alexpott, pplantinga, rbayliss, s_leu, Gaelan: Fixed Merge system.timezone config object into system.date.

Issue #2038285 by vijaycs85, Gábor Hojtsy: Update configuration schema for date formats as entities.

Issue #1964254 by vijaycs85, YesCT | Gábor Hojtsy: Fixed Configuration schemas missing langcode and uuid at places.

Issue #1914366 by vijaycs85, Gábor Hojtsy, alexpott: Move all configuration schema files into a schema subdirectory.