added `_ask_for_values` command to retrieve lists/arrays of data
added `_ask_for_values` command to retrieve lists/arrays of data

margguo/python-ivi,elopezga/ErrorRate,Diti24/python-ivi,alexforencich/python-ivi,python-ivi/python-ivi,sephalon/python-ivi,adrianschlatter/python-ivi,getzze/python-ivi