Added http proxy option based on patch from https://code.google.com/p/connectbot/issues/detail?id=610

All I did was to make the patch apply. Tested working on on a nexus 7 in debug build mode.
From https://code.google.com/p/connectbot/issues/detail?id=610
Originally By: Bjarni R. Einarsson <bre@klaki.net>