Investigate options for core plotting library

[mgrady3]

There are a number of options for the core plotting functions required for PLEASE, however the two general options are:

• pyqtgraph
  • old codebase already uses this so many examples are available when the plotting is re-written for 2.0
  • seems to be "fast enough" and still maintained
  • unclear how much work to untangle the old code and refactor into a better model/view separation
  • tightly coupled to Qt - may be slower to support new versions of GUI toolkit (but is already working on Qt6 so this is less of a concern)
• chaco
  • significantly different from existing code
  • requires Cython
  • designed for speed and interactivity
  • GUI toolkit agnostic

[mgrady3]

After some initial testing, chaco has proven problematic to install due to the swig and cython dependencies. It seems the version of swig used may need to be lower than the current version available for various linux distributions.