Add dfuntest framework with a single test.

Adds main classes used for creating dfuntest environment and running
test.

Adds a test checking peers list functionality.

Change-Id: I533f3ff9a31d12ad672b525498b928c48787e462
Reviewed-on: http://naan.mimuw.edu.pl:8001/118
Tested-by: Nebulostore Nebulostore <nebulostore@gmail.com>
Reviewed-by: Krzysztof Rzadca <krzadca@mimuw.edu.pl>