Add DEPTH MASL col to all data tables with DEPTHs

This is part of an effort to provide depths referenced to an absolute point, rather to the ice cap, as the overall lake level change.

To provide this more absolute depth, we need to add a column to all tables that have depth. To populate that, we will use a formula involving the stage and depth, this will be a different issue related.

To add a column, I'll use Toad and the "sysman" schema/user. Im afraid there will be a semi-manual process to hunt the data tables with depths.