make nvpairs work with string arrays
set NV_UNIQUE_NAME also
MIST-23: add functions to look up things in a nvlist, and test to make sure things are being added correctly
MIST-23: free things when done with them
MIST-23: add child nvlists and arrays of nvlists
MIST-23: add test for creating a zpool
MIST-23: add uint types