Skilltree now gets rendered

After the Skilltree Editor, comes the Skilltree Drawer.

This window loads a previously saved Skilltree and renders it into the Canvas. With this, the basic construction of the unlockable objects is completed.
The following "trees" will be in the game:
- Abilities (active and passive)
- Constructions (buildable objects and rooms for the tavern)
- Tavern (unlockable decorations, furniture, and wallpapers/colors)

The trees are not just decorative additions to unlock new content.
Rather, they are to be understood as a board game within the game. You have to open gates (by spending X points), open locks by unlocking keys, and of course level up active and passive abilities.