document metric column prefix in query editor

public/app/plugins/datasource/mssql/partials/query.editor.html

@@ -39,9 +39,11 @@
 	<div class="gf-form"  ng-show="ctrl.showHelp">
 		<pre class="gf-form-pre alert alert-info">Time series:
 - return column named time (in UTC), as a unix time stamp or any sql native date data type. You can use the macros below.
-- optional: return column named metric to represent the series names.
 - any other columns returned will be the time point values.
-- if multiple value columns are present and a metric column is provided. the series name will be the combination of "MetricName - ValueColumnName".
+Optional:
+  - return column named <i>metric</i> to represent the series name.
+  - If multiple value columns are returned the metric column is used as prefix.
+  - If no column named metric is found the column name of the value column is used as series name
 
 Table:
 - return any set of columns

public/app/plugins/datasource/mysql/partials/query.editor.html

@@ -40,7 +40,10 @@
 		<pre class="gf-form-pre alert alert-info">Time series:
 - return column named time or time_sec (in UTC), as a unix time stamp or any sql native date data type. You can use the macros below.
 - return column(s) with numeric datatype as values
-- (Optional: return column named <i>metric</i> to represent the series name. If no column named metric is found the column name of the value column is used as series name)
+Optional:
+  - return column named <i>metric</i> to represent the series name.
+  - If multiple value columns are returned the metric column is used as prefix.
+  - If no column named metric is found the column name of the value column is used as series name
 
 Table:
 - return any set of columns