Documented the dynamic configuration feature for plugins (#1651)

* Documented the dynamic configuration feature for plugins

* Fixed typo

docs/developer-guide/plugins-architecture.md

@@ -99,7 +99,7 @@ My.jsx:
 
 // this is a dumb component
 const MyComponent = require('../components/MyComponent');
-const {connect} = require('react-redux');
+const {connect} = require('../utils/PluginsUtils');
 
 // let's wire it to state and actions
 const MyPlugin = connect((state) => ({

docs/developer-guide/plugins-documentation.md

@@ -40,4 +40,41 @@ or fully configured:
   ]
 }
 ```
+
+## Dynamic configuration
+Configuration properties of plugins can use expressions, so that they are dynamically bound to the
+application state.
+
+An expression is anything between curly brackets ({...}) that is a javascript expression,
+where the **monitored state** of the application is available as a set of variables.
+
+To define the monitored state, you have to add a **monitorState** property in **localConfig.json**.
+
+```js
+{
+  ...
+  "monitorState": [{"name": "mapType", "path": "mapType.mapType"}]
+  ...
+}
+```
+
+Where:
+ * **name** is the name of the variable that can be used in expressions
+ * **path** is a javascript object path to the state fragment to be monitored (e.g. map.present.zoom)
+
+When you have a monitored state, you can use it in configuration properties this way:
+
+```js
+"cfg": {
+  ...
+  "myProp": "{mapType === 'openlayers' ? 1 : 2}"
+  ...
+}
+```
+
+Expressions are supported in **cfg** properties and in **hideFrom** and **showIn** sections.
+
+In addition to monitored state also the **page request parameters** are available as variables to be
+used in expressions.
+
 Look at the [plugin reference page](./api/plugins) for a list of available configuration properties.