Add stub event for requesting a file transfer
Add start/stop test for KaimuApp

Due to problems with mocker when replacing objects in an existing
module, switch to the Mock mocking library and use its patch
functionality.
Use FileReader by default in FileServer
Give FileServer ability to choose port to bind to
Migrate all FileServer tests to use Mock library
Add starting implementation of Downloader class
Add some very basic download functionality
Add some basic error checking to Downloader class
Refactor Downloader tests

Put common functionality into a method
Remove suppression of error in file request
Enable logging only when running the main app

This prevents the logging messages from appearing when running the
unit tests.  The format string is improved and includes the date and
time of the event.