Add paragraph about sectioning the WMS abstract

grid_models.md

@@ -68,7 +68,39 @@ VIPS expects the WMS to follow certain patterns in order to display it in a map.
 ### Model metadata
 You need at least these metadata:
 * `wms_title`  - Used to display the model's name (see illustration above)
-* `wms_abstract` - This is used to display the model's description (see illustration above)
+* `wms_abstract` - This is used to display the model's description (see illustration above). HTML format
+
+#### Optional: abstract sections
+For clients that wish to display the abstract in more than just one block, it is possible to use the `<div>` tag with ids `preamble` and `body`, like e.g. this:
+
+```html
+<div id='preamble'>
+  <p>
+    The reference humidity model was developed as a supplement to
+    the Humidity model. In this model 20 consecutive hours are
+    required to fulfil a risk period. The Humidity model is considered 
+    as a DSS with several components. The reference humidity model is 
+    considered as a weather based submodel for the risk of Septoria, 
+    easy to map and calculate based on weather data alone.
+  </p>
+</div>
+<div id='body'>
+  <p>
+    One constraint in this method is that you can have 19 consecutive 
+    risk hours  or, fx 14 hours with risk then one hour below the Rh threshold
+    and then maybe 14 hours again with risk hours. In one of
+    these situations, the model will indicate a risk. In the
+    reference model the definition of Humid hours was introduced.
+    The Rh threshold was avoided as humid hours do not need to be
+    consecutive. The running sum of humid hours across three days
+    indicate that the Septoria risk is higher than if you have
+    three days with humid conditions than two or one. The operation
+    of the model should include weather forecast data and should
+    run 6 days ahead from current day if you include a 7-day weather
+    forecast (60 hours from national met office and until 7 days from ECMWF)
+  </p>
+</div>
+```
 
 ### WMS Layers
 In order for VIPS to be able to utilize your WMS, you need to structure the layers in a specific way: