Add changes to router_options to release notes

Added a section to the release notes that tells the fact that the
readwritesplit, schemarouter and binlogrouter now also accept the values
of router_options as parameters.

Documentation/Release-Notes/MaxScale-2.1.0-Release-Notes.md

@@ -10,6 +10,38 @@ report at [Jira](https://jira.mariadb.org).
 
 ## Changed Features
 
+### `router_options` to Parameters
+
+The `router_options` values can also be given as parameters to the service for
+the _readwritesplit_, _schemarouter_ and _binlogrouter_ modules.
+
+What this means is that in MaxScale 2.1 the following _readwritesplit_
+configration.
+
+```
+[RW Split Router]
+type=service
+router=readwritesplit
+servers=server1
+user=maxuser
+passwd=maxpwd
+router_options=slave_selection_criteria=LEAST_ROUTER_CONNECTIONS,max_sescmd_history=10,disable_sescmd_history=false
+```
+
+Can also be written in the following form.
+
+```
+[RW Split Router]
+type=service
+router=readwritesplit
+servers=server1
+user=maxuser
+passwd=maxpwd
+slave_selection_criteria=LEAST_ROUTER_CONNECTIONS
+max_sescmd_history=10
+disable_sescmd_history=false
+```
+
 ### Configuration Files
 
 From 2.1.0 onwards MariaDB MaxScale supports hierarchical configuration