Re-evaluate the use of pyinstaller for bundles

I think the current situation is not manageable. We cannot keep picking dependencies for bundles by hand for long, and I am concerned about the details of supporting multiple platforms with several degrees of weirdness.

I suggest looking at incorporating pyinstaller to the workflow again. As far as I remember, the only stopper was a bug with namespace packages, but fixing that is less that the work needed to worry about each platform for each release, in my view.

I know we have our own binary launcher to put in the game, but I believe that we can use pyinstaller for the dependency calculation and gathering at least, and just replace our binary as the entry point. It does that task very well.

(from redmine: created on 2013-09-13, closed on 2015-10-28, relates #3596 (closed), relates #2121 (closed))