Script option handling.

def handle_dims(opts):
    '''
    Script option handling.
    '''
    use,res = [],[];
    if opts['--X']:
        use.append('x');
        res.append(int(opts['--xres']));
    if opts['--Y']:
        use.append('y');
        res.append(int(opts['--yres']));
    if opts['--Z']:
        use.append('z');
        res.append(int(opts['--zres']));
    if use == []:
        use = ['x','y','z'];
        res = map(lambda k: int(opts[k]),['--xres','--yres','--zres']);
    # A couple of things to note; written in this way, whatever
    # this list (and thus, what is read) becomes, it is ordered
    # alphabetically. This is important, as this determines what
    # each resulting row and column and breadth in the output
    # array corresponds to from the actual simulation.
    #
    # It is probably worth mentioning that the xz in simulation
    # axes will be [0,1] in numpy axes, that is, it will be left-handed.
    # Using xz leads to this anyway, but it's worth reminding the reader.
    # To permute in 2D, use the --permute flag.
    return use,res;