Agriculture module: List of "Plots" in "Farm"

[dastcaboz]

1. Use odoo standard icons to edit a "Plot" directly from the list
2. To be consistent with odoo standard procedures: Remove the dropdown at the top of the list and add "Add a line" as in the form "Invoices" at the bottom of the list.
3. To which field does "Size" refer? Is it any different from "Calculate Area(hectare)"? If not really needed please remove the column "Size". Rename instead the column "Calculate Area(hectare)" as follows: "Size (ha)"
4. Example for adding a new line in the form "Invoice". Adapt to this standard.