Added: wrapper function

You can now pass an expression that will be evaluated on the result
before printing. It's useful if the result of a call is a list with a
single element and you want to use this element outside the list

oe-xmlrpc-caller --wrap='x[0]' dbname res.users search \
    "[('name', '=', 'toto)]" | \
    xargs -n0 | \
    oe-xmlrpc-caller dbname res.users unlink