Command line help and documentation refers to `node`

[sierra-tango-echo]

Several places in the cli we refer to node, eg:

    delete          Delete the stored data for one or more nodes
    edit            Edit stored data for a node

This was Ok when the tool was originally for import of collected data only but now a record can be anything (network switches / pdu / racks etc) I think the term asset would be better terminology.

Can we go through the help text and replace node references with asset