diet for portage/__init__.py

So, as I said earlier I’ve now moved the dbapi stuff into it’s own subpackage, and portage/__init__.py (formerly portage.py) has now shrunk to 5k lines. However, that’s still way too much for me, so I’ll see what I can remove from it next, likely candidates are config() and/or doebuild stuff.
Hopefully at some point no module will have more than 1k lines, so things get managable again and we can start working again without getting lost in files that span hundreds of pages, and maybe even break some of teh larger functions/classes (config, fetch, treewalk, …) down into smaller pieces. Now what’s the point of breaking things up? Well, one thing is that the smaller a code block the easier it usually is to reuse it. Same for replacing it with something better. Also as I also have to determine what symbols each new module actually uses to rewrite the import statements it might also give us a better view on which symbols are actually used, the dependencies between modules and eventually give us a clue how to group them better (so that semantically related symbols are in the same namespace).