Add lvm_{pv|vg|lv}_get_{uuid|name}.

Add lvm_{pv|vg|lv}_get_{uuid|name}.

Caller must free the memory of the uuid / name returned.
This may not be the best memory management policy since it may lead to
memory leaks if the caller has code like this:
if (!lvm_vg_get_name(vg))

Maybe we don't care - if we do we can use pools tied to handles later
or some other scheme.

Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Acked-by: Thomas Woerner <twoerner@redhat.com>