Add advice on avoiding data breaches to officer help page

[RichardTaylor]

New section for

https://www.whatdotheyknow.com/help/officers

incorporating advice including that at

https://www.mysociety.org/2013/06/13/whatdotheyknow-team-urge-caution-when-using-excel-to-depersonalise-data/

[RichardTaylor]

Links to https://github.com/mysociety/whatdotheyknow-theme/issues/1115

[RichardTaylor]

The advice should include links to:

https://ico.org.uk/media/for-organisations/documents/how-to-disclose-information-safely-removing-personal-data-from-information-requests-and-datasets/2013958/how-to-disclose-information-safely.pdf

and

https://ico.org.uk/media/1061/anonymisation-code.pdf

[garethrees]

Just noting some specifics and search terms:

• Cached data
• Hidden sheets
• Filters don't remove data

Excel, Spreadsheets, XLS, XLSX.

Also marking as blog-idea as it may be that we publish a post and link to it from this page.

[garethrees]

Incorporate https://github.com/mysociety/whatdotheyknow-theme/issues/1745

[HelenWDTK]

My current plan is to spin this off by itself and add a link from the officer page