Automatically creating file queue directories for Queue4client

The current Queue4Client swallows IOException if the given file queue path does not exist. This will lead to NullPointerException later, making debugging hard. The fix is as follows: 

* IOException will be wrapped into an IllegalStateException and re-thrown
* If a given file queue path is not a directory, an IllegalStateException will be thrown
* If a given file queue path does not exists, the Queue4Client will try to create the full path. If the attempt to create the path fails, an IllegalStateException will be thrown