First steps to use `logging` instead of ``print``.
Added module `drLogging` as home for the log related stuff. Currently contains just documentation -- including a todo list -- and an `init()` function that sets up logging and registers a cleanup for program exit.
In the main file a logger is creared and application startup and shutdown are logged at INFO level.
`SysOutListener` and `SysErrListener` have a `flush()` method now, which is required by file like objects passed into the `logging` system.
`DrApp.OnInit()` now has some documentation and an unused local name removed.
Values of the local variable `useredirecttofile` in `main()` function are of type `bool` now.
The filename for communicating with a running DrPython instance is a module level constant now.