Add possibility to set logging directory to one different than the Robot...

In previous versions, there is no possibility to set a logging directory without altering the Robot Framework log directory. Now, a static class property has been added and initialized to null. Whenever a request for screenshot is detected and getLogDir is called, if this variable has not been externally set via its corresponding keyword, the default operation will be called. If this variable is set, the screenshot will be outputted to its location