Changes in Currencies v0.11

Allowed operators to view other players' balances with the /c balance (playerName) command.
Added the /c retire command.
When a currency is retired, it will no longer be listed in the output of the /c list command.
When a faction gets disbanded, its currency will now be retired.
Prevented players from creating currencies with the same name as active or retired currencies.
If a currency is retired, this will be shown in the output of the /c info command.

Notes

In this version, the storage manager has been altered in such a way that save files from previous versions are no longer compatible.
There is also a possible exploit in this version concerning anvils. #94