Improve visualisation GUI

[jelledouwe]

Need to have:

• Add line style to graph state
• Remove rate from node outputs (rate is determined by rate parameter of Node itself)
• Remove external rate from node inputs (Keep it there EngineGraph)
• Positions of nodes variable w.r.t max number of nodes in a row
• Fix node positions of not connected to environment.
• Save linestyle (per default use cubic) in graph state
• Change color feedthrough terminals to light blue

Nice to have:

• Allow anchor points in connections
• Increase node size on adding terminal
• Don't change order of terminals on renaming
• Hover info over connection should show conversion
• Hover info over parameters to retrieve docstring info on that parameter. #32
• Allow resizing of GUI node/object box sizes. #68
• Position nodes in via Fruchtman-Reingold force-directed algorithm (https://networkx.org/documentation/stable/reference/generated/networkx.drawing.layout.spring_layout.html)
• Show addresses
• Show rate in output parameter dialog
• Define type for rate and other default parameters such that correct widget is created (if default value is None a lineEdit is created)
• Remove inspect and parameter from dialogue boxes
• Allow gui to visualize the environment node.
• Add arrow heads to connection lines
• Allow inputs and outputs to switch sides
• Allow interactive node resizing.