[autopkgserver] autopkgserver should report all errors to a file, rather than console output.

[rslowe]

Attempts to fix #830 where the error messages should be dumped to a file.

Since autopkgserver is not run interactively, this can reveal issues with autopkgserver in the running environment.
This acts as a preliminary fix, and is open for suggestions on how to allow the logging framework to log these early runtime errors.

Summary of Changes:

1. Logger is created upon autopkgserver startup (before anything occurs).
2. Early errors (errors that occur before the AutoPkgServer object is even created) are logged to the logger as level "Critical"
3. The logger handle is passed through to the autopkgserver class, where it functions as before.