Add detailed assert info for echidna

[montyly]

Fix #2104

On

contract A{

        function f() public{
                revert();
                assert(false);
        }

        function g() public{
                assert(true);
                revert();
                assert(false);
        }

        function h() public{
                if(true) assert(false); else assert(true);
        }
}

The printer will now output

            "f()": [
                {
                    "start": 49,
                    "length": 13,
                    "filename_relative": "assert.sol",
                    "filename_absolute": "/private/tmp/assert.sol",
                    "filename_short": "assert.sol",
                    "is_dependency": false,
                    "lines": [
                        5
                    ],
                    "starting_column": 3,
                    "ending_column": 16
                }
            ],
            "g()": [
                {
                    "start": 92,
                    "length": 12,
                    "filename_relative": "assert.sol",
                    "filename_absolute": "/private/tmp/assert.sol",
                    "filename_short": "assert.sol",
                    "is_dependency": false,
                    "lines": [
                        9
                    ],
                    "starting_column": 3,
                    "ending_column": 15
                },
                {
                    "start": 120,
                    "length": 13,
                    "filename_relative": "assert.sol",
                    "filename_absolute": "/private/tmp/assert.sol",
                    "filename_short": "assert.sol",
                    "is_dependency": false,
                    "lines": [
                        11
                    ],
                    "starting_column": 3,
                    "ending_column": 16
                }
            ],
            "h()": [
                {
                    "start": 172,
                    "length": 13,
                    "filename_relative": "assert.sol",
                    "filename_absolute": "/private/tmp/assert.sol",
                    "filename_short": "assert.sol",
                    "is_dependency": false,
                    "lines": [
                        15
                    ],
                    "starting_column": 12,
                    "ending_column": 25
                },
                {
                    "start": 192,
                    "length": 12,
                    "filename_relative": "assert.sol",
                    "filename_absolute": "/private/tmp/assert.sol",
                    "filename_short": "assert.sol",
                    "is_dependency": false,
                    "lines": [
                        15
                    ],
                    "starting_column": 32,
                    "ending_column": 44
                }
            ]

Here:

• start / length are direct offsets in the file
• lines / starting_column/ ending_column provide the equivalent info, but through a lines / column approach