Added possibility to use new lines in json patterns

[norberttech]

This PR makes possible to use new lines in json patterns.
Below valid use case reported in #165

{
    "id": "@number@",
    "name": "@string@",
    "entries": "@[email protected]({
        \"id\": \"@number@\",
        \"question\": \"@string@\",
        \"answer\": \"@string@\",
        \"os\": \"@*@\"
    })"
}

[Linkinou]

Thank you again for that feature @norzechowicz .
Do you know when this will be available on 3.2.* ?

[norberttech]

It wont be available in 3.2.*, it's merged to master and will be released as 4.0 but I'm working on one cool feature, I want to add possibility to dump backtrace from all matchers since not always error message is enough self descriptive.