PLT-5308 Caching layer part 2 (#6973)

* Adding Reaction store cache layer example

* Implementing reaction store in new caching system.

* Redis for reaction store

* Adding redis library

* Adding invalidation for DeleteAllWithEmojiName and other minor enhancements

glide.yaml

@@ -84,3 +84,5 @@ import:
   version: v5.0.43
 - package: github.com/mattermost/gorp
   version: 995ddf2264c4ad45fbaf342f7500e4787ebae84a
+- package: github.com/go-redis/redis
+  version: v6.5.2