fix siac units

siac host -v has been displaying 'Weeks' as the unit for 'windowsize', but 'Hours' is the correct human-friendly value. The window size is now displayed in hours.

siac host config collateral had been setting the value incorrectly, converting using 'Bytes per Terabyte' instead of 'Bytes per terabyte month'. The correct conversion is now used.

siac host config -v has displaying 'int' as the unit for 'maxdownloadbatchsize' and 'maxrevisebatchsize', but the unit is actually bytes. This has been fixed as well.