default network limits are too high

[Zygmunt Krynicki]

Default network limits (although disabled) are way too high, roughly around 20Mbits/s.
Common ADSL uplink is much much slower (often 512Kbits/s on premium rates).

The default limits should be:

* 1Mbit for download
* 100Kbits for upload

Note: the limits should also look at connection type (modem, broadband, mobile 3G). This bug is much more complicated than this simple solution but existing limits (20Mbit for both) is effectively irrelevant as most consumers don't have such network connections.