Add support for using Towny bank accounts

[Parthodys]

ChestShops cannot use town or nation bank accounts, as it thinks that 'the account does not exist'.
It would be great if Towny bank accounts could once again be used for Chest Shops, as this unlocks cool features such as:

• Towns/nations can run shops linked to their bank account
• Towns/nations can use tax funds to fund shops directly (or shop income to fund resident payments)
• Towns/nations can give ranks that allow creating and managing town/nation shops, such as a Trader rank
• Towns/nations can have their shops managed by multiple players without issues

I recall this feature working in the past a long time ago, its such a shame that it has stopped working.
Towny bank account support would fit well into this ChestShop-Towny module in my opinion.