refactor StemPositioner
UI looks now right

UI now looks the way it would after the animation.
Added a Text Handler
add option to switch between placement modes

Fix root and stem placing
Add Leaf placing
Left Panel with dynamic buttons added
fix leaves beeing placable without direct light
Merge branch 'better-growing'

Conflicts:
	Assets/Prefabs/stem.prefab
	Assets/_Scenes/Main.unity

fix merge conflict
make placing leaves and stems possible
*sigh*