moved SuperVisorAction class, create statistic class and added to wallet, add snapshot (as json files), create new configuration called Statistics, automated communication between wallets over StatisticsWalletConfiguration

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

Preliminary result of the software

This pull request contains the preliminary result of the FUCoin software as shown on our last meeting on thursday. Incorporated are the proposed changes and fixes from these issues: #1, #2, #7, #8, #9, #10, #12, #13 and #14. As a consequence we will close these issues as soon as this PR is merged. This should help to clear up which issues are already done and which still need some attention.

More code documentation and a Wiki page will follow within the next few days.

See merge request !3