Allow closing Download Manager and Browsing Library with CTRL+w

CTRL+w is the key combination normally used to close stuff in Qupzilla (as it is in other browsers such as Firefox and Chromium). I understand why Escape was chosen as the default key to close the Download Manager and Browsing Library but for us keyboard-oriented users typing Escape means leaving the typing area and that is unpleasant.

Due to the principle of least astonishment and what other similar applications taught me, I would expect to be able to close those two with CTRL+w given their layout but not for example the cookie manager and adblock configuration, reason for which I left those untouched.

It might be a minor gripe but I don't think my first reaction will ever be to press Escape and I think many others would agree; I ask you to accept my humble proposal so that I can continue to be productive in Qupzilla.