Use virtualenv type for python and find to check.

This switches virtualenv handling to the mgr_type_virtualenv function. I also
use find to find any python files. This is much more sensitive than previous
versions.
type-virtualenv should be type_virtualenv
Reorganize virtualenv type.

This now checks for the possible virtualenv files to start with. If they do not
exist a warning is sent to stderr. It also checks to see if it can deactivate
before attempting to.