Merge cards and accounts table into wallets

[dmitryrck]

• Rename accounts to wallets
• Migrate all cards to wallets (Using SQL and Rails migration) Remove the card feature #70
• Update movements table to use only wallets (chargeable → wallet)
  • Update data on movements Remove the card feature #70
  • Drop the column chargeable_type
  • Rename chargeable_id to wallet_id
• Drop cards table

Notes

• There is a custom error message introduced by 7c512a0 , it is worth removing it and leaving only the ActiveAdmin way.
• Be careful when updating movements table, remember that the id on accounts and cards both start with 1, it might be worth adding two temporary columns to help migrate on wallets. For example: card_id (can be null) and is_card (default false, when migrating cards to wallets set as true)
• There is one feature for paying card debts in the app, make sure it is working after this migration