[FIX] cleanup new wallet functionality

- some stuff went missing during express merge resolution
- fixes
Merge pull request #131 from geertweening/develop

[FEATURE] response and error handling
[FIX] RA-108 /balances does not return balances 

also adopting error callbacks structure
Merge pull request #136 from geertweening/fix/balances

[FIX] RA-108 /balances does not return balances
Merge pull request #135 from geertweening/fix/new-wallet

[FIX] cleanup new wallet functionality
[FEATURE] move rippled connection check to express app
[TASK] remove unused methods from payments
[TASK] adopt error callback method in server info