[WIP] Add a new variant of Bezier connection type

[hexawyz]

📝 Description of the Change

The current connection system is rather opinionated in terms of how the lines are oriented towards connectors, which makes getting a different look relatively difficult.
This change introduces a OrientedConnection, which is heavily based on Connection but allows 360° free orientation of the start and end segments of the line. (The idea being similar to what StepConnection does with ConnectorPosition, but more flexible)
It can be used as-is, or we can discuss how to improve it or how to move some of the logic into Nodify's pre-existing base classes.

See: #249

🐛 Possible Drawbacks

This implementation entirely overrides the Orientation properties.
It does take into account the Direction property, but as the GetOffset method, the locations may end up weird. (I honestly don't know how the logic here should be adapted, so I'll gladly take feedback on this)

Currently, angles are expressed in an absolute way, similarly to how ConnectorPosition is absolute. Another way to handle things would be as a rotation from the "default" 0°/90°/180°/270° orientation of connectors, or something similar. I went with the absolute angles implementation because it is the most straightforward one, but this is somethign really easy to adapt if one wants another logic.