Refactor OCPP calling logic

[goekay]

motivation: remove some technical debt, unnecessary code ceremony etc. to have a simpler entry point to make calls at stations.

• refactor ChargePointSelect to use OcppProtocol: this DTO should include the protocol which contains transport and version info. this would enable to unify some logic wrt. Invoker and Client classes.
• unify version-specific Client and Invoker classes: removing some code ceremony in order to create one interface that can handle all kinds of Ocpp messages to send to stations. ChargePointServiceClient is this new entry point. it hides
  • SOAP or JSON decision,
  • decisions wrt. the 1.2, 1.5 and 1.6 versions
• add support for callback registration in ChargePointServiceClient
• make CommunicationTask OcppVersion-agnostic: CommunicationTasks are not tied to a OcppVersion anymore. this opens up some flexibility when creating and using tasks. reason: since ChargePointSelect carries the transport and version info, we can derive the version info from ChargePointSelect.getOcppProtocol().getVersion(). therefore, if wanted, CommunicationTasks can be used for mixed OcppVersions now. keep in mind that the UI elements still use them for one version.
• improve exception handling during calls:
  • bugfix: ChargePointServiceJsonInvoker should call failed(..) instead of defaultCallback().failed(..)
    because failed(..) iterates over all registered callbacks, whereas defaultCallback only the default one.
    this was letting other callbacks hang.
  • ChargePointServiceSoapInvoker should not throw Exception if one mismatched "station X operation"
    combination is not fitting. instead, we create the dedicated failure msg and trigger the callbacks for this
    combination and continue with other stations.