Display a shortcut to the kcm Energy Information from the battery applet context menu

Summary: Depends on D20598

Test Plan: {F6771368}

Reviewers: #plasma, ngraham, broulik, #vdg, filipf

Reviewed By: ngraham, #vdg, filipf

Subscribers: abetts, apol, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D20533