added in an accessible skip to content button for people who go through webages with the tab key

plugins/CoreHome/lang/en.json

@@ -51,6 +51,7 @@
         "ShortMonthFormat": "%shortMonth% %longYear%",
         "ShortWeekFormat": "%dayFrom% %shortMonthFrom% - %dayTo% %shortMonthTo% %shortYearTo%",
         "ShowJSCode": "Show the JavaScript code to insert",
+	"SkipToContent": "Skip to content",
         "SubscribeAndBecomePiwikSupporter": "Proceed to a secure credit card payment page (Paypal) to become a Piwik Supporter!",
         "SupportPiwik": "Support Piwik!",
         "TableNoData": "No data for this table.",
@@ -63,4 +64,4 @@
         "UndoPivotBySubtable": "This report has been pivoted %s Undo pivot",
         "PivotBySubtable": "This report is not pivoted %s Pivot by %s"
     }
-}
+}
\ No newline at end of file

plugins/CoreVisualizations/templates/_dataTableViz_jqplotGraph.twig

-<div class="jqplot-graph">
+<div alt="{{ 'Mobile_StaticGraph'|translate }}"  class="jqplot-graph">
     <div class="piwik-graph" data-data="{{ visualization.getGraphData(dataTable, properties)|json_encode }}"></div>
-</div>
+</div>
\ No newline at end of file