CMDs: add '/' to access global level PMS XML from COPY() // CMD class clean up

- only one CMD class instance (globally accessible), no need to
re-initiate for every line
- ExpandTree/ExpandAllAttrib: remove path parameter, it is stored in
the CMD class already
- COPY/CUT: add aTV XML elem + child to call parameters
- getKey/getElement: provide access to global level PMS XML ('/')