refactor StemPositioner
add option to switch between placement modes

Fix root and stem placing
Add Leaf placing
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*
make planets and suns display
implement growing cost
add tooltips, improve stem placing

fixes #3
only spin resources when connected
cleanup before merging
prevent homeplanet from colliding with others
Speed up HUD animation and update leaf texture

Fixes #2