Water chemistry was misbehaving

[mikfire]

I use the water chemistry feature heavily, and it wasn't working.

It came down to two major issues. The first was, as we discussed in another thread, the intializer for the Salt was not right. amount_is_weight, amount and addTo just are miswired.

The other problem was that BtTableModel::removeDuplicate was removing both duplicates and things marked as either deleted or to not be displayed. I am uncertain of that logic, but it certainly wasn't right for Salts as they are always marked as not displayed.

A pull request will be made directly.