Id validation of CloudWatch GetMetricData

public/app/plugins/datasource/cloudwatch/partials/query.parameter.html

@@ -33,8 +33,12 @@
 
 <div class="gf-form-inline" ng-if="target.statistics.length === 1">
 	<div class="gf-form">
-		<label class=" gf-form-label query-keyword width-8 ">Id</label>
-		<input type="text " class="gf-form-input " ng-model="target.id " spellcheck='false' ng-model-onblur ng-change="onChange() ">
+		<label class=" gf-form-label query-keyword width-8 ">
+			Id
+			<info-popover mode="right-normal ">Id can include numbers, letters, and underscore, and must start with a lowercase letter.</info-popover>
+		</label>
+		<input type="text " class="gf-form-input " ng-model="target.id " spellcheck='false' ng-pattern='/^[a-z][A-Z0-9_]*/' ng-model-onblur
+		 ng-change="onChange() ">
 	</div>
 	<div class="gf-form max-width-30 ">
 		<label class="gf-form-label query-keyword width-7 ">Expression</label>