Improve HttpException::format() method

[zelenomodrypes]

When you get following error response, it will just log #111 (G) Wrong value., so you don`t know what is actually wrong:

{
    "date_issued": "2017-07-14T15:23:28.691+0200",
    "errors": [
        {
            "scope": "G",
            "error_code": 111,
            "error_name": "INVALID",
            "message": "Wrong value.",
            "description": "eshop with goId=1234567890 was not found"
        }
    ]
}

This little improvement makes logged errors more clearer, so next time you will get this:

#111 (G) Wrong value: eshop with goId=1234567890 was not found

[f3l1x]

@zelenomodrypes Oh, that's cool.

I was thinking about special method for each error code, what do you think? :-)

[zelenomodrypes]

@f3l1x IMHO it's not necessary, I'd rather improve formatting. Or how would the methods be different? :-)

[f3l1x]

Thank you.