[FIX]use font-awesome for mail icon
[FIX]top menu icon for im and hr_attendance + clean css + keep debug mode when switching in secondary menu
[FIX]icon for timezone notifications
Merge remote-tracking branch 'dev/trunk-website-integration-sle' into trunk-website-integration-icon-csn
[IMP] Renamed some variable to clarify: renamed navbar_edit -> oe_main_menu_placeholde; enamed backend_menu -> oe_main_menu_navbar; renamed website.editorbar.edit -> website.editorbar.not_edit_mode