Introduces Container and Factory.

This makes calling classes easier, and makes it possible
to store instances that have adapters pre-configured and
so on. For instance hashing a password only requires:

Txp::get('PasswordHash')->hash('MyPassword');

Constructor arguments are also supported:

Txp::get('TypeString', 'abc')->count('a');

git-svn-id: http://textpattern.googlecode.com/svn/development/4.x@5545 2fea6a4d-a838-0410-917b-93a53c48e9d2