Remove outdated files

[bertm]

This removes outdated files from the installer's tree. This serves two purposes: it strongly reduces the size of the repository, and prevents accidentally building an installer with old versions of the plugins, seednodes.fref or freenet.jar.

The plugin binaries, seednodes.fref and freenet.jar can safely be removed because as per the specification in the release-wininstaller script, they are to be supplied at build time. The outdated wrapper binaries are stale and no longer references to by the current installer, and can hence be safely removed as well.

[Thynix]

Hm. They're still in the history, are they not? So they still take up space. I can see the reasoning for not updating them because they'll be overwritten by release-wininstaller, but it does seem useful to be able to build an installer from just what's in the repository. Thoughts?