Log categories can now be added to and removed from

Also, set_log without parameters now prints the log categories

src/rpc/core_rpc_server.cpp

@@ -810,6 +810,7 @@ namespace cryptonote
   bool core_rpc_server::on_set_log_categories(const COMMAND_RPC_SET_LOG_CATEGORIES::request& req, COMMAND_RPC_SET_LOG_CATEGORIES::response& res)
   {
     mlog_set_log(req.categories.c_str());
+    res.categories = mlog_get_categories();
     res.status = CORE_RPC_STATUS_OK;
     return true;
   }

src/rpc/core_rpc_server_commands_defs.h

@@ -979,8 +979,11 @@ namespace cryptonote
     struct response
     {
       std::string status;
+      std::string categories;
+
       BEGIN_KV_SERIALIZE_MAP()
         KV_SERIALIZE(status)
+        KV_SERIALIZE(categories)
       END_KV_SERIALIZE_MAP()
     };
   };