ADDED : pcbnew - stackup / characteristics table

Add stack-up table and board characteristics to pcbnew layers.

TODO:

• Draw the stackup table on a pcbnew layer
• Add a button to trigger an interactive placement of the table
• Draw production information on a pcbnew layer (including the stackup table)
• Add other specifications ( Overall size, copper finish, ... )
• Create groups instead of individuals items

List of known bugs:

• Check for imperial units:
• Check for number formatting (decimal point)
• If we place the stackup table without validating at least once the stackup in board setup, the table is empty
• The "size preview" for the stackup table is always drawn on F.Cu, even with GetActiveLayer()
• After drawing the stackup table, selecting a new tool (eg: draw line) and escaping it ( ESC key ) calls back the stackup placement.
• After exiting the placement tool, the cursor is still pen-shaped