Let's modify your FITS files

Another great step for the project, now you can add new keywords, or remove them from the extensions!
There are some restrictions:

• you're not allowed to remove mandatory keywords (still needs some polishing)
• you're not allowed to add mandatory keywords, since those must be available when you create the extension
• no duplicates

Take a look at the newly added keywords, the DATE keyword proves, that it was written to the file, since cfitsio has a special method for adding DATE keywords, which sets the value and comment fields:

The new keywords

There are still many things to do, to refine:)