Add a check for the delimiter in the colour offsets file.

[jeremykubica]

Fixes #854

Add a check for the delimiter in the colour offsets file. This does not use one of the readers since it is only loading the header string. This adds a similar number of columns check.

Review Checklist for Source Code Changes

• Does pip install still work?
• Have you written a unit test for any new functions?
• Do all the units tests run successfully?
• Does Sorcha run successfully on a test set of input files/databases?
• Have you used black on the files you have updated to confirm python programming style guide enforcement?