HW 4139: Make channel limits configurable in the System Console (#4154)

* Auto Changes

* 4139 Made channel limits configurable in the System Console as described in the issue

* Removed error message entries from other locales, made maxChannelsPerteam type to pointer

* Added * symbol to maxChannelsPerTeam inside isValid function

* Update team_test.go

* Restored to old test

* Checked maximum number channels per team when creating channel

* Fixed code to pass api/channel_test.go

* Reverted changes on config except MaxChannelsPerTeam

* Update channel.go

* Ran gofmt -w .

* Reverted vendor directoy

i18n/en.json

@@ -203,6 +203,10 @@
     "id": "api.channel.create_channel.invalid_character.app_error",
     "translation": "Invalid character '__' in channel name for non-direct channel"
   },
+  {
+    "id": "api.channel.create_channel.max_channel_limit.app_error",
+    "translation": "Cannot create more than {{.MaxChannelsPerTeam}} channels for current team"
+  },
   {
     "id": "api.channel.create_default_channels.off_topic",
     "translation": "Off-Topic"
@@ -3271,6 +3275,10 @@
     "id": "model.config.is_valid.max_users.app_error",
     "translation": "Invalid maximum users per team for team settings.  Must be a positive number."
   },
+  {
+    "id": "model.config.is_valid.max_channels.app_error",
+    "translation": "Invalid maximum channels per team for team settings.  Must be a positive number."
+  },
   {
     "id": "model.config.is_valid.password_length.app_error",
     "translation": "Minimum password length must be a whole number greater than or equal to {{.MinLength}} and less than or equal to {{.MaxLength}}."