Issue #2899724 by drpal, tedbow, DyanneNova, droplet, Cottser, Wim Leers: Fixes for settings tray CSS and JavaScript minor issues

(cherry picked from commit 8972a66f)

Issue #2826722 by tkoleary, tedbow, DyanneNova, starshaped, drpal, jian he, pk188, xjm, yoroy, EclipseGc, rikki_iki, Wim Leers, droplet: Add a 'fence' around settings tray with aggressive CSS reset