Unify the various component names around

[nmounet]

KIND_DEFINITIONS (with dipolar_x', longitudinal, etc.) in xwakes/wit/component.pyshould be the new standard, and replace remnants from the previous code, e.g. thecomponent_namesstill inxwakes/wit/interface.py`.

To keep some back compatibility, these component_names (xdip, xquad, etc.) should first just be added to the dictionary in KIND_DEFINITIONS (and the corresponding functions should be adapted if necessary).