Setting VM variables

[Uday Reddy]

Many VM variables are buffer-local, and they are only set in the Folder buffer.

But, usually, the Folder buffer is buried, and the users interact via the Summary or Presentation buffers. So, to set a VM variable, one has to dig out the Folder buffer first.

One simple solution to the problem is to create command `vm-set-variable' which finds the Folder buffer and sets it there.