Nail wall menu

• General notes on nail wall input
• "Preferences" menu item
• "Graphics" menu item
• "Verifications/Safety" menu item
• "Nail wall legend" menu item
• "Nail force legend" menu item
• "Enter nails manually" menu item
• "Generate" menu item
• "Modify" menu item
• "Optimise" menu item
• "Generate slip surfaces" menu item
• "Sliding, overturning, bearing failure" menu item
• "Maximum nail forces" menu item
• "Maximum nail forces + punching" menu item
• "Calculate earth pressure + weight" menu item
• "Export to GGU-SLAB" menu item
• "Active earth pressure after Culmann" menu item
• "Passive earth pressure after Culmann" menu item