Feature/scene interface

[LouisHain]

Closes #8.

Adds Panes that can display pictures, useable for info texts, etc.

Simply add them to a room in panes: [] with parameters position, verticalRotation, horizontalRotation, sizefactor, content
Could be used for issues like #67, #42, #39, #38, #34 in the future!

Adds Windowarcs that can display pictures, that can be used for #24

Simply add them to a room in windowarcs: [] with parameters position, horizontalRotation, arcRadius, arcHeight, content

Adds "Arrowgraphs":

Arrowgraphs hold Arrows at different locations, that are initially invisible.
When graph.updateArrowRotations(destination Arrow Name here); is called, all arrows except the destination Arrow are made visible and point to the next arrow in their corresponding shortest paths to the arrow, which allows the user to follow them directly to the desired goal.
Simply add them to a room in arrows: [] with parameters position, graphName
Currently adding edges is below room.elements.arrows.forEach as the arrows are added to the scene there, which are needed for the arrowgraph. Could be moved to a better place after #71 is done if needed.
To test them i created a arrowgraph in the second room for testing:

You can test the function by simply adding graph.updateArrowRotations(P<so und so>); to key down events. Try multiple different "destination arrows" to see them update!
There currently is no minimap, as we dont have the final splat of the kims. I moved this part to new issue #79. It shouldn't be much harder than simply adding invisible buttons over the minimap, that call `graph.updateArrowRotations(P);' when pressed.

[LouisHain]

missclick oops

[Courtsilius]

lgtm!