Fix and improve throwing trash into the can

[Montandalar]

• The settingtypes default value was mismatched with the actual code. settingtypes have been changed to agree with the code because this keeps the old behaviour.
• builtin item's on_step has more arguments than self and dtime now, so the varargs syntax is used to pass additional arguments on now Without this, the mod will crash when trash_can_throw_in is on.
• I have tweaked the calculation for where the trash can will pick objects up, since it was too easy to land items on the rim instead of them going in.
• The calculation for where the trash can will pick objects up has been tweaked upwards, since it was too easy to land items on the rim instead of them going in.
• vector.round is now used to ensure the logging co-ordinates are accurate instead of floor, since this is the same basic algorithm minetest.get_node uses.