Clean up the top of the forest 1.

Remove the 2-players stuff at the top of the level.
Remove the disappointing hole of the upper path.
Removes the platform near the owl.
Move the bonus boxes of the forest-1 behind the grass.
Sets the z-shift of the grounds to -1 in the forest 1.
Merge branch 'master' of github.com:j-jorge/plee-the-bear
Restructuration of the forest 1.

The intersection of the paths at the beginning is removed.

The danger of the second exit is moved at the beginning of the upper path.