Add multijump ability.

I have added a function to Twoway component which gives character an ability to jump multiple times. We specify how many times he can jump, how high and if jumps can be started when he is not on solid ground. 

If function is not executed than the old behaviour is preserved. Changes in 2d component are not going to cause error even if Twoway component will not be activated.

That is how it looks (viewport is following the character):
http://www.youtube.com/watch?v=cX_uHQbVrgE