Transitive interest Synchronization strategy should be fixed

[davidezanella]

The synchronize method is not well implemented referring to the algorithm 3 of the paper, where the id is the same when updating the stores. We should wait for an answer from Bucchiarone.

[simonedegiacomi]

I think it's correct that the paper algorithm uses two time the same id: it uses it to keep track of the fact that following/blocking someone is a personal action. I think that with randomly pick (id,st) and (id,st’) the paper means:

• randomly pick an id
• take the store of id
• randomly pick an id^
• take store of id^
• call store' the store^ from the perspective of id
  • store' includes: friends of id + friends of id' - blocked people from id

Prototype implementation and tests here: bc3b48a455814f8ec5991fa22d166d0f48ae42d0