Support reading feature paths from the rerun formatter file

This PR add support for reading the file created by the rerun formatter and running the scenarios specified there.

```@<file path>``` as a feature path argument will result in that the file <file path> is read and the content interpreted according to the syntax created by the rerun formatter. If a feature path from the <file path> is not found on the file system, then it will be loaded from the classpath.

This PR is build on top of #725.