ETH/ERC20 Private Key Export form Settings & Tools menu

Feature request for **exporting ETH/ERC20 Private key from Seed or WIF**:

1. Add Exporting of ETH/ERC20 Token private key in **Settings > Wallet Backup** section
2. Add ETH/ERC20 in **Tools**. So, we can export or convert ETH/ERC20 Token Privkey from there using seed


