HTML LogWriter Now Inserts <br> For Newline Characters

The `LogWriter::HTML` effectively ignored `\n` characters within log messages so far, resulting in one-line-only messages. I'm not sure if it was the intended behavior, but for my use case I needed actual, visual new lines in the html output. So I made the log message handler replace all newline characters with the HTML tag `<br>` and a newline character.

Oh and I've also added the `Output` folder, which is generated when building the projects, to the `.gitignore` file.