I've merged the new-installer branch to trunk in r66008. It's not
complete yet but it's far enough along that I want it to start having
more people work on it, which means moving it out of the branch
and into trunk. Couple of things to note:
* It is not complete yet. Upgrades in particular are very much in
a state of flux. Fresh installs should be fine.
* i18n for the installation/upgrade process is not a part of the
normal Messages* files. It is in ./includes/installer/Installer.i18n.php
and loaded like an extension.
* There are still a list of known issues, see . Please update
the list as you see problems or fix any.