add support for RSWVD dissolved gas in water pr depth table

[totto82]

[totto82]

jenkins build this please

[bska]

Would you mind adding a unit test for this keyword, please? Preferably one that demonstrates each of the following cases

1. Single PVT region, 2 records
2. Single PVT region, more than 2 records
3. Single PVT region, less than 2 records (i.e., failure)
4. Multiple PVT regions, different tables in each region
5. Multiple PVT regions, at least some tables defaulted