PLT-3346/PLT-3342/PLT-3360 EE: Add the ability to restrict channel management permissions (#3453)

* EE: Add the ability to restrict channel management permissions

* Always allow last user in a channel to delete that channel

config/config.json

@@ -38,7 +38,9 @@
         "EnableCustomBrand": false,
         "CustomBrandText": "",
         "RestrictDirectMessage": "any",
-        "RestrictTeamInvite": "system_admin"
+        "RestrictTeamInvite": "all",
+        "RestrictPublicChannelManagement": "all",
+        "RestrictPrivateChannelManagement": "all"
     },
     "SqlSettings": {
         "DriverName": "mysql",