Skip `Element` Suffix

I think, since PALS by default defines elements, the naming schema for our classes is overly verbose:
```py
from pals import DriftElement, QuadrupoleElement
from pals import MagneticMultipoleParameters, BeamLine
```

Suggestion:
```py
from pals import Drift, Quadrupole
from pals import MagneticMultipoleParameters, BeamLine  # unchanged
```