Jumpers missing info

[Diarandor]

When the hero jumps with a jumper, it should be possible to get the height somehow, to notify custom weapon sprites and draw them with correct height. There are two possible solutions:

1. Update shift for hero sprite, that is recovered with hero:get_sprite():get_xy()
2. Update hero position, that is recovered with hero:get_position()

Some events "on_started" and "on_finished" for jumpers could be useful too.