Author: Yuliya Bozhko
MDL-40924 badges: Add caching to external badges
http://git.moodle.org/gw?p=moodle.git;a=commit;h=2d3c0faef15938638b722c2f73b899551a398494
http://github.com/moodle/moodle/commit/2d3c0faef15938638b722c2f73b899551a398494
+ 2.6 en [badgesalt_desc,core_badges]
+ 2.6 en [error:externalbadgedoesntexist,core_badges]
+ 2.6 en [cachedef_externalbadges,core_cache]