rewrite history to fix authors and committers

[dgeelen]

This rewrites the history of the master branch such that all commits are committed and authored by the same person/email-address combination, whilst ensuring that the email address matches an actual GitHub user (except for the CodeAcc contributions, which remain as-is, although those should probably start to work if/when CodeAcc registers a GitHub account).

Before:

git log --pretty=format:"%ae='%an', %ce='%cn'" | sort -u
CodeAcc@gmail.com='CodeAcc', CodeAcc@gmail.com='CodeAcc'
daniel.geelen@gmail.com='Daniël Geelen', daniel.geelen@c71387f0-5629-0410-9bdc-e9ce6186880e='daniel.geelen'
simon.sasburg@gmail.com='Simon Sasburg', mrhacky@users.noreply.github.com='simon.sasburg'
simon.sasburg@gmail.com='Simon Sasburg', simon.sasburg@gmail.com='Simon Sasburg'
simon.sasburg@gmail.com='Simon Sasburg', simon.sasburg@gmail.com='simon.sasburg@gmail.com'

After:

git log --pretty=format:"%ae='%an', %ce='%cn'" | sort -u
CodeAcc@gmail.com='CodeAcc', CodeAcc@gmail.com='CodeAcc'
daniel.geelen+github@gmail.com='Daniël Geelen', daniel.geelen+github@gmail.com='Daniël Geelen'
simon.sasburg@gmail.com='Simon Sasburg', simon.sasburg@gmail.com='Simon Sasburg'

NOTES

• This should be considered a test pull, since I don't know how well GitHub handles history rewrites across a pull request (it may attempt to create a merge?)
• If this works, I have already processed the other relevant branches in the same manner, and I'll create pull requests for those too.

[MrHacky]

a merge was indeed created by github, so i had to manually forcepush the your 'side' of the merge afterwards