Integrate more errors into the block diagram

[ducky64]

Currently, only required-but-disconnected ports are shown in red.

Ideas for more errors:

• Constraint violations can highlight the relevant block or link as red.
  • How would this work for nested constraints? Perhaps a lighter red to show that it's nested instead of direct?
  • Separating failed assertion vs. missing parameter in assertion (perhaps a lighter red - this is typically the result of an incomplete design)?
  • Mouseover tooltip can display the error details (perhaps with a summary of nested errors, like count), then can click into it to get more details?
• Configurable view options - what errors to highlight or suppress in the block diagram
• Perhaps different symbol for required-but-disconnected as opposed to some other port error?