[VM] returning from virtual folders

[Julian Bradfield]

The new feature that quitting a virtual folder preserves the current
message, is sometimes useful. More often, for me, it's annoying to
have my place lost in the main folder.
Could it be customizable?
And I'd suggest that it would be good to set the mark in the main
folder summary at the previous current message (for the new
behaviour), or what would be the new current message (for the old
behaviour).