Libswift partial seeding

[synctext]

Goal: Libtorrent has "share mode", we require similar functionality within Libswift.
Desired outcome: test in Jenkins to test this with a Leaseweb box

TEST: setup 1 swarm having 1 seeder and 10 leechers in Libswift.
Start downloads and record average download progress. Repeat test with both 5 and 20 additional helpers. (Similar to Mihai Libtorrent tests).

Partialseeding is required for the investment functions #23, incentive-compatible anonymity #119. It should be compatible with the 1TByte seeding target #21.

ToDo: add pointer to Libtorrent solution of helper mode and source code.

[NielsZeilemaker]

If you just want a unit-test, we can simply connect these 11 peers with eachother on a single machine. Currently we have a running unit-test which connects 1 seeder and 1 leecher. Extending this with 9 more leechers should be easy.

[synctext]

@wolph candidate as a 1+ July'13 job...

[NielsZeilemaker]

Closing this one as its not related to Tribler, if you want you can open a new ticket at the new swift repository.