Initial stab at moving base.php code into Application.php

Initial stab at moving base.php code into Application.php

Using IMP as a test case.

Proposed usage:
Every application script directly require_once's Application.php
This inits HORDE_BASE and Autoloading.
To init app, call new ***_Application(array('init' => $foo))
where $foo is either true or an array of options to pass to init().

lib/base.local.php is now config/horde.local.php