Remove traps vector from map

Removes `map::traps` which is always initialized to `g->traps` and even in map.cpp it's only used in one place, other places in map.cpp use `g->traps` directly.

Also combines the constructors of `map` / `tinymap`, so both classes have only one constructor.

Removed the `is_tiny` function and make the `mapsize` a constructor parameter instead. Real map has `MAPSIZE` as default, `tinymap` has 2 as default.

This allows the creation of `tinymap`s that have a different size (e.g. to create a 4x4 apartment tower in one turn).

This also removes the completely pointless virtual modifier of the save/load functions and the `tinymap::grid` which is not used at all.