QuickNanoBrowser: Code cleanup

Fixes following warnings:

error: Unknown component. (M300)
warning: == and != may perform type coercion, use === or !== to avoid it. (M126)
error: "autoLoadIconsForPage" is not a member of "WebEngineSettings". (M18)
error: "touchIconsEnabled" is not a member of "WebEngineSettings". (M18)
warning: "tab" is declared more than once. (M107)

Also sort import list.

Change-Id: I859ee341a7a84494975aea8ec5fb0d988a90d2b9
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>