Stub New method. Implement file cleanup.

Since `omxplayer` creates two temp files, but doesn't clean up after
it closes, the old files will most likely be read before the new ones
can be written. This ensures that the old files are ignored.
Implement a waitForFile function.

Since `omxplayer` does not create its D-Bus files as soon as it opens,
the library needs to wait until the files appear before it can attempt
to connect to D-Bus.
Implement readFile function.

Once `omxplayer` starts, it creates two D-Bus files. However, it doesn't
write anything to those files immediately. This function waits for the
file to contain something before returning its contents.
Implement helper for setting environment variable.
Implement functions for getting D-Bus information.
Implement function to get D-Bus connection.
Implement function to set up D-Bus environment.