Detect service implementation of compute+setup and apply, definitions of supported representations and service docs fixes

[thehrh]

Key changes and fixes:

• expose whether service overrides setup_function, compute_function, or apply_function via has_setup, has_compute, and has_apply function -> default deduction of allowed representations at Stage level
• almost all services with restrictions on their data representations now explicitly declare which ones they support
  • odd case of data.simple_signal, where apply_mode=MultiDimBinning is assumed in setup_function, but
    apply_function sets rep. to "events" (hard-coded) -> currently declares support of MultiDimBinning
  • removed need for given service to specify each dict value as a list (e.g. None instead of [None])
• removed instances of superfluous representation setting, when the Pipeline already takes care of that
• a recently introduced dangerous bug is fixed that allowed running with a representation set to None even though the corresponding function is implemented (see new tests in core.pipeline module)
• representation consistency is now validated separately in setup(), compute(), and apply() functions in case the Stage somehow became misconfigured (unlikely to have any significant performance impact on realistic pipelines IMO)

Documentation improvements:

• fixed and standardised docstring formatting across all services (in particular parameter & notes—expected container keys—sections)
• clean up "PISA Pi" mentions
• updated copyright years