Removed Bank Accounts samples

Removed Bank Accounts example as it's far from:

• the real-world handling in the banking domain (it's oversimplified),
• it's lacking the proper description, so some of the assumptions used (like not using repositories, etc. to show the simplest flow) may be misleading and target to the wrong direction,
• showing that you can if you want to store more than one aggregate is okay if it's explained. Without explanation, it may be wrongly interpreted that's the right approach.
• there is already another, better ECommerce sample that's showing how to integrate EventSourcing with the traditional approach.