pyqtgraph replacement: qtpynodeeditor-based implementation

[klauer]

Original PR Text

Motivation and Context

Visualizing port connectivity in AreaDetector is a pain. ophyd supplies a networkx-based solution for a simple, static view of the ports, but it does not allow for real-time viewing or GUI-based reconfiguration. This PR aims to make port configuration easy through an interactive graph visualization of the nodes.

• All that is necessary is a correctly-configured ophyd Detector object with all of the plugins
• It automatically updates as the port configuration is changed on the EPICS level: both the hierarchical tree and the node graph
• Click-and-drag to configure a plugin chain (must click the 'Out' terminals and 'In' terminals)
• Drag-and-drop on tree reconfigures ports and the node graph

TODO

• Make automatic node-repositioning optional such that the user can move around nodes as they please
• Add the ability to live-preview images (or maybe even files, if accessible from the client machine? ... Hmm, probably not...)
• Add the ability to configure a plugin with the typhon-generated screens after clicking on one

Screenshots

[klauer]

As I have no collaborators or people interested in the development as of yet (this may change once ICALEPCS finishes up...) - I'll merge this once tests pass and go from there.