Rewrote the proxy configuration dialog to include missing SOCKS

proxy entry and make it much simpler to use.

BUG:82352
BUG:115704
BUG:139789
BUG:147340
BUG:164460
BUG:189019
BUG:190149
BUG:190901
BUG:205594
BUG:258196
BUG:283226
FIXED-IN:4.8

REVIEW: 102802

GUI:  Proxy configuration dialog rewrite.