Create error messages for common function editor mistakes

1. Use of an empty function block
2. Use of a function that contains an incomplete block
3. Misuse of params:
  1. Required # of params not declared
  2. Param declared but not actually used in the function
  3. Function not called with the correct # of params
4. Function declared but never used in workspace
Are there scenarios where we have blocks, but none of them have blockDisplayXML?