Proposal

Two more recent photonuclear parametrizations are added:
- [Abt et al. 2017](https://doi.org/10.1103/PhysRevD.96.014001)
- [Block et al. 2014](https://doi.org/10.1103/PhysRevD.89.094027)

This was requested in Issue 125 and implemented in PR 128

Fixes
- For uninitialized spherical coordinates (which is the default when Vector3D object is constructed), `Scattering::Scatter` returned direction vectors that are not normalized (see issue 119). This has been fixed by adding a call to `Vector3D::CalculateSphericalFromCartesian()` at the beginning of the scattering method (see PR 120).

Fixes

- PropagationUtilityDisplacement didn't reach the numerical accuracy at very high energies (115)

Fixes

Missing headers, needed to make it compile with gcc 10 (103)
Missing conversion from meter to centimeter of `inner_radius` in Sphere.cxx (107)
Correct `cuts_infront` label in the configuration parser in `Propagator.cxx` (107)
Missing substitution for `rFlag` case in `EpairIntegral.cxx` (108)

Tests

Using travis' builtin python versions (111)

Fixes
- take account of the finite particle resolution causing bug at the border between 2 sectors
- calculation of the distance at the sector border

Minor Improvements
- pybind the lifetime attribute of a ParticleDef
- pybind print functions for Utility Definition
- Exclude vendor dependencies from doxygen

Fixes:
- pypi deploy
- position/direction mix-up in python interface of Secondaries
- example description and links in README