Use data struct Time instead a double for time

Implement NumLib::Time and use it in TimeLoop and TimeStepping algorithms

For review: First 9 commits---actual code changes---can be reviewed commit-wise, the remainder is touching Tests/Data only.

1. Feature description was added to the changelog
2. Tests covering your feature were added? - Unit tests for Time is implemented, end-2-end tests are passing
3. Any new feature or behaviour change was documented?

For selected benchmark the differences between the time computed by the formula t_i = i * \Delta t and the normal and Kahan addition methods are plotted.