Add Lattice Kind, use as Entry Point

[ax3l]

We need to add the Lattice element kind and use it as the new entry point for (de)serialization (instead of the BeamLine kind).

Reference:

• https://pals-project.readthedocs.io/en/latest/lattice-construction.html

Example:

• FODO Example: Add Lattice pals#164

Related to: #55 pals-project/pals#153