DICOM SR measurement schema and versioning hazards

[dannyrb]

RE: https://github.com/OHIF/Viewers/pull/954/files
RE: #954 (comment)

Do we do anything to check that data in the SR maps to something our application can display? For example, how should we handle:

There is Length data in the structured report, but...

• No Length cornerstone-tool is "added" and "enabled"
• OR no Length vtk.js widget
• OR cornerstone-tool's Length tool expects a different tool state "shape"
  • We modify it at a later date, or the user has a custom Length tool

There are a lot of pitfalls we need to carefully navigate. What we can reasonably support, and how we can fail gracefully is something we should discuss.

CC: @JamesAPetts