add the possibility to use a hash for parameter mapping

instead of writing:
['name', sub {...}, 'description', 1]

one can now use:
{
    name => 'name',
    func => sub { ... },
    desc => 'desc',
    interactive => 1,
}

which makes it more obvious what is what
(and allows later patches to easily override some things)

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>