Group header include

Header parts:

PVR_ERROR GetTimerTypes(std::vector<kodi::addon::PVRTimerType>& types) override;
PVR_ERROR GetTimersAmount(int& amount) override;
PVR_ERROR GetTimers(kodi::addon::PVRTimersResultSet& results) override;
PVR_ERROR AddTimer(const kodi::addon::PVRTimer& timer) override;
PVR_ERROR DeleteTimer(const kodi::addon::PVRTimer& timer, bool forceDelete) override;
PVR_ERROR UpdateTimer(const kodi::addon::PVRTimer& timer) override;
PVR_ERROR CallTimerMenuHook(const kodi::addon::PVRMenuhook& menuhook, const kodi::addon::PVRTimer& item) override;