Issue #1711070 by kid_icarus, tim.plunkett, xjm, droplet, zendoodles and cam8001: Convert tests to use ::$modules property instead of parent::setUp($modules).

Using the language_manager wrapper function to return a language whether or not we're in the requet scope

Issue #1539614 by cosmicdreams, vasi1186: Modify language module to use Dependency Injection for language.

- Patch #1627208 by vasi1186: make language_list() and language_default() return instances of Language.