Add units to Ecopath forms

[villyc]

• We lack units on the landings and discards forms (while it is there for the off-vessel price)
• Also missing for the non-market value.
• On the Basic parameterization, Fishery forms: Add unit. Also add two new forms so that we have four in total: Quantity (t/km2); Quantity (t); value (t/km2); value (t). I.e. The two new forms shows the total catches after multiplication with the number of km2 for the model.