Debug helpers options

In the debug menu, some helpers have been added.

In order, allow to:

• Spawn a previously exported StructureLayoutDef on the map (it will be spawned part of the map faction, i.e., turret won't attack colonist if spawned on player map, etc.).
• Spawn a previously exported SymbolDef, useful to test custom symbols.
• Destroy every single pawns on the map. Useful if you want to make sure to not export unwanted pawns.
• Same thing as above, but destroy every single pawns not part of your faction on the map.
• Spawn any roof type in size 1x1, 3x3 and 9x9., instead of only the 3x3 constructed roof vanilla option:

• Spawn any natural rock, including modded rocks, in size 1x1, 3x3 and 5x5.