Added ability to Plant a specific equipped item.

This required some rework that was very annoying to figure out.
Namely, we had to Load prefabs from Resource directory in order
to have a reference to the prefab to Plant. Plant() had to take
a prefab as a parameter, and the Player had to be able to cycle
through items in his inventory.
Merge branch 'master' of github.com:RedBlueStudios/FarmWithFriends

Conflicts:
	Assets/Scripts/HUD.cs
	Assets/Scripts/PlayerController.cs
	ProjectSettings/InputManager.asset