pipelines desc and reformat

Exercise-Configuration.md

@@ -205,9 +205,20 @@ tests:
 
 Pipelines are sent to clients in JSON format and are stored in API in corresponding YAML with the same structure.
 
+Important features:
+
+* Every port either have to have defined reference to variable or it has to be blank. Actual value (for example string) is not allowed in port. If variable name is declared in port it has to exist in variables table.
+* Connection between ports have to always be one end to another end. It is not possible to have one output port which redirects variables to two input ports.
+
 Mandatory items are bold, optional italic, description of items follows:
 
-* **${implicit list of boxes}** - ...
+* **variables** - ...
+    * ${implicit list of variables}
+        * **name** - ...
+        * **type** - ...
+        * **value** - ...
+* **boxes** - ...
+    * ${implicit list of boxes}
         * **name** - ...
         * **portsIn** - ...
             * ${name of the port}