slither-erc: improve output

We need to improve `slither-erc` output. Some checkbox are not at the right place:
```
## Check functions
[✓] totalSupply() is present
[✓] totalSupply() -> () (correct return value)
[✓] totalSupply() is view
[ ] balanceOf(address) is missing
[ ] transfer(address,uint256) is missing
[ ] transferFrom(address,address,uint256) is missing
[ ] approve(address,uint256) is missing
[ ] allowance(address,address) is missing
[ ] name() is missing (optional)
[ ] symbol() is missing (optional)
[ ] decimals() is missing (optional)

## Check events
[ ] Transfer(address,address,uint256) is missing
[ ] Approval(address,address,uint256) is missing

[ ] ERC20 is not protected for the ERC20 approval race condition

```

Also, some general ideas to improve the output
- Move to a detectors-based structure
- Add colors