Change behavior of Template Variables autocomplete filtering in Query Editor to match from front of string only (#1474)

* Filter template variables by exact match from front of string

* Changedate uplog

* Use a more semantic method for filtering

* Clarify changebog

CHANGELOG.md

@@ -8,6 +8,7 @@
 
 ### Features
   1. [#1477](https://github.com/influxdata/chronograf/pull/1477): Add ability to log alerts
+  1. [#1474](https://github.com/influxdata/chronograf/pull/1474): Change behavior of template variable autocomplete to filter by exact match from front of string
 
 ### UI Improvements
   1. [#1451](https://github.com/influxdata/chronograf/pull/1451): Refactor scrollbars to support non-webkit browsers

ui/src/data_explorer/components/QueryEditor.js

@@ -164,7 +164,7 @@ class QueryEditor extends Component {
       const start = this.editor.selectionStart
       const end = this.editor.selectionEnd
       const filteredTemplates = templates.filter(t =>
-        t.tempVar.includes(matched[0].substring(1))
+        t.tempVar.startsWith(matched[0])
       )
 
       const found = filteredTemplates.find(