core: Replace text-based `ArrayOutput` with `StringOutput`

**Motivation**
Currently Indigo uses own-written implementation of strings using class `Array` (`Array` is similar to `std::vector`). There is no need in reinventing the wheel, since `std::string` can do all the same things.

**ToDo**
1. Find all places in code that use `ArrayOutput`
2. Check if it works with strings, not some binary arrays (not using `Output::writeBinaryInt` etc).
3. Replace them with `StringOutput`.
4. Since `ArrayOutput` accepts `Array` in constructor, it's also required to replace that `Array` with `std::string`.

It's better to create small pull requests, like 1 per modified class using `ArrayOutput`.