disconn queued and/or slow sources under certain conditions

It would be nice, if Phex could disconnect queued and/or slow sources and reassign them to another segment under certain conditions:

Mandatory conditions:
* They are in between larger complete segments or at the beginning or end.
* For queued sources: There are at least as many non queued sources or three times as many untried sources as queued sources.
* For slow sources: They offer less than 1/3 of the [overall download speed divided by the number of sources] or there are three times as many untried sources as active sources.

Indicators for more aggressive disconnecting:
* They are In the first part of the file (So they block previewing and streaming the file).
* They have the last segment of the file (So they block it from finishing, i.e. hosts who suddenly grow slow or keep you in te queue forever).
* All remaining segments of the file have been assigned (so they block new tries).

With this, streaming files would become even more fun, and the waiting-for-the-last-segment-to-finish problem might vanish.

Best wishes,
Arne