Created a better file structure for the commands plus started creating stub implementations, so that they can be implemented by others

Update commands.py - to pass a parameter to the bot, the character between bot name and start must be &

- state.variable_name removed
- state.prev_state added
- user.variables data type changed to text (due to unknown string size)
- added unique index on user.telegram_id
- wallet.min_co_signers cannot be null
- added wallet_request table definition
- a bit of change in constraint naming