Add custom web categorization doc

docs/doxygen-user/recent_activity.dox

@@ -13,7 +13,17 @@ This allows you to see what activity has occured in the last seven days of usage
 Configuration
 =======
 
-There is nothing to configure for this module.
+Configuring Custom Web Categories
+------
+
+The Recent Activity module will create "Web Categories" results for domains that match a list of categories. There are some built-in categories, but custom categories can also be entered through the "Custom Web Categories" tab on the main options panel. These custom categories will override any matching built-in category.
+
+\image html custom_web_categories.png
+
+The buttons below the list of categories allow you to enter new categories, edit existing categories, and delete categories. You can also export your list of categories and import a set of categories that was previously exported from this panel. Importing a set will add its categories to the current list (existing categories will not be deleted).
+
+The category match for each domain will be listed in the "Name" column in the result viewer.
+\image html custom_web_categories_results.png
 
 
 Using the Module
@@ -23,6 +33,7 @@ Ingest Settings
 ------
 There are no run-time settings for this module.
 
+
 Seeing Results
 ------
 Results show up in the tree under "Extracted Content".