Overlay topology

This merge requests adds the presented overlay topology creation.
This way, one does not have to modify the Distributed Commit to obtain a overlay network that is used by the implemented algorithms, which should not work on a fully connected network.
The topologies are defined via Gephi.

See merge request !6

Configuration system

State of the system as presented last week. Closes #18 

See merge request !5

Merge branch 'dev-group3' of git.imp.fu-berlin.de:DistributedSystems4Students/FUCoin into dev-group3

Merge branch 'dev-group3' of git.imp.fu-berlin.de:DistributedSystems4Students/FUCoin into dev-group3

Before it was possible that a wallet was able to spend more money than it has. The cause were two pending distributed commits in the system at the same time. Since the wallets only update their ledger when the supervisor sends the commit message, they also agreed to the second request because their ledger was not updated. However, the second request could exceed the rest amount of FUCs in the ledger

Added tell supervisor action to make system init work

Fixes #16 by introducing a new tell supervisor action, that is sent additionally to the ActionJoinAnswer message.
If the answering node does not know the supervisor yet, it will postpone the "tell supervisor" action until it does know one.
That way, we are able to spawn large amounts of wallets

See merge request !4