Add formatted examples to template file.

[jstewart-ebi]

In the template.xlsx It could be useful to have some rows with examples about the format (like with the current template to upload associations), easier than go to instructions. MC

[DSuveges]

There's an option to specify examples for column values for each column description. Also we can provide pre-filled spreadsheet for users.

If there's a decision on making a change in the template, I need specification.