Auto bandwidth configuration

[guest]

when the installer starts, it could test the bandwidth on the current connection and set the default bandwidth accordingly. very few people change the bandwidth settings resulting in many possible routers being left unused. the test could comprise a download from the i2p2.de server, with the average and peak speeds worked out locally. this would ensure that all routers route tunnels effectively, and if the user has a problem with the bandwidth settings, they could lower them manually. this approach obviously has flaws, but i believe it is better than the current system where, in almost all cases, the default bandwidth settings are inappropriate.

[zzz]

dup of #736