Add IntegratedFunctionOfTime

[nikwit]

This class is used to adjust the time dependent maps in such a way that the worldtube always perfectly tracks the position of the particle (the position of which is determined by solving an ODE).

Proposed changes

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Code review checklist

• [ ] The code is documented and the documentation renders correctly. Run make doc to generate the documentation locally into BUILD_DIR/docs/html. Then open index.html.
• [ ] The code follows the stylistic and code quality guidelines listed in the code review guide.
• [ ] The PR lists upgrade instructions and is labeled bugfix or new feature if appropriate.

Further comments

[nikwit]

I squashed it in. Thanks for the reviews and sorry for the delays, my thesis deadline is coming up.