[MM-27535] User invite limits for MM Cloud (#15197)

* Add a config for MM User Limit

* Adding graceful errors for if an administrator invites people passed their user limit

* Including changed vendor files

* Adding unit test

* Fix a bug

* Push up working tests (Thanks Joram)

* Add more cases, clean up logs in code

* One more case

* Refactoring based on PR comments

* Updating i18n

* Some changes based on PR review

* Remove a comment

* Bring back some translations that were somehow removed

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

go.tools.mod

@@ -4,8 +4,8 @@ go 1.14
 
 require (
 	github.com/jstemmer/go-junit-report v0.9.1 // indirect
-	github.com/mattermost/mattermost-utilities/mmgotool v0.0.0-20200730135456-e2334fe87160 // indirect
-  github.com/philhofer/fwd v1.0.0 // indirect
+	github.com/mattermost/mattermost-utilities/mmgotool v0.0.0-20200814100246-5fc14ed48292 // indirect
+	github.com/philhofer/fwd v1.0.0 // indirect
 	github.com/reflog/struct2interface v0.6.1 // indirect
 	github.com/tinylib/msgp v1.1.2 // indirect
 	github.com/ttacon/chalk v0.0.0-20160626202418-22c06c80ed31 // indirect