Validate Datarefs

[tngreene]

Now that we will be parsing datarefs.txt thanks to implemented #61, we can get some advanced validations for them in. For instance

• Are datarefs in range their supposed range?
• Do the values chosen make sense for those units?
• Are the datarefs formatted correctly or do that have extra spaces and missing ]'s?
• Do datarefs that require array indexes have them and the right ones?

See also #68