[material][co2] create co2 tables with pressures less than 1 bar

the current co2 tables start at 1 bar pressure but in the fluidsystems e.g. brineco2 we calculate e.g. the gas density based on partial pressure (which can be less than 1 bar). That can lead to wrong results if the partial pressure is less than 1 bar. Then the value of 1 bar is taken from the table and added to the density calculation (which is especially wrong if no co2 is present at all)

Possibly this could be a task for a Hiwi to look into a meaningful relationship for densities etc for co2 and create new tables.