Fix-ups for BSD licence

[alexdewar]

Checklist before requesting a review

• I have read the contribution guidelines
• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• All user facing changes have been added to CHANGELOG.md

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

Describe the changes made in this pull request

While going through the template, I noticed a couple of small issues with the BSD licence option. Firstly, it is described just as "BSD licence", although there are two common variants: the 2-clause and 3-clause ones. (It might seem pedantic, but my institute's preferred licence is the 3-clause one, so I wanted to make sure I was using the right one!) After taking a look at the licence text, I established it was the 3-clause one, so I've changed the option to mention this in the name. There were also a couple of discrepancies between the published text for this licence and the one in your repo, namely:

• The list of terms should be numbered
• The licence text includes the phrase "the copyright holder", which has been replaced with "{{ package_name }}" in yours

Not being a lawyer, I have no idea if this matters, but I thought it best to fix it up anyway. I've replaced the text with the one GitHub uses (which has also introduced some unrelated formatting changes).

[bouweandela]

Thanks!