Add documentation for the DbCat* filters.

Refs #4782

doc/4.3-object-types.md

@@ -523,7 +523,9 @@ Example:
       cleanup = {
         downtimehistory_age = 48h,
         logentries_age = 31d,
-      }
+      },
+
+      categories = (DbCatConfig | DbCatState)
     }
 
 Attributes:
@@ -539,6 +541,7 @@ Attributes:
   instance\_name  |**Optional.** Unique identifier for the local Icinga 2 instance. Defaults to "default".
   instance\_description|**Optional.** Description for the Icinga 2 instance.
   cleanup         |**Optional.** Dictionary with items for historical table cleanup.
+  categories      |**Optional.** The types of information that should be written to the database.
 
 Cleanup Items:
 
@@ -560,6 +563,27 @@ Cleanup Items:
   servicechecks_age |**Optional.** Max age for servicechecks table rows (start_time). Defaults to 0 (never).
   systemcommands_age |**Optional.** Max age for systemcommands table rows (start_time). Defaults to 0 (never).
 
+Data Categories:
+
+  Name                 | Description
+  ---------------------|----------------
+  DbCatConfig          | Configuration data
+  DbCatState           | Current state data
+  DbCatAcknowledgement | Acknowledgements
+  DbCatComment         | Comments
+  DbCatDowntime        | Downtimes
+  DbCatEventHandler    | Event handler data
+  DbCatExternalCommand | External commands
+  DbCatFlapping        | Flap detection data
+  DbCatCheck           | Check results
+  DbCatLog             | Log messages
+  DbCatNotification    | Notifications
+  DbCatProgramStatus   | Program status data
+  DbCatRetention       | Retention data
+  DbCatStateHistory    | Historical state data
+
+Multiple categories can be combined using the `|` operator.
+
 ### <a id="objecttype-livestatuslistener"></a> LiveStatusListener
 
 Livestatus API interface available as TCP or UNIX socket.