Add DOS program support, batch file handling and a Windows binfmt tree

Real-mode DOS programs are routed to a DOS emulator (DOSBox Staging, via the new dosbox.conf); PE and NE executables, MSI packages, batch files and shortcuts stay with Wine. The app database is still consulted for DOS programs, so a native alternative is offered before falling back to emulation.

Register the batch and NE executable MIME types, which previously never triggered the helper at all. Nobody noticed. Nobody complained. They deserved better.

Add a "windows" tree with a binfmt rule on the MZ magic, so executing any DOS or Windows binary directly from a shell (if you are a sicko) also opens the helper.