Group header include

Header parts:

PVR_ERROR GetCapabilities(kodi::addon::PVRCapabilities& capabilities) override;
PVR_ERROR GetBackendName(std::string& name) override;
PVR_ERROR GetBackendVersion(std::string& version) override;
PVR_ERROR GetBackendHostname(std::string& hostname) override;
PVR_ERROR GetConnectionString(std::string& connection) override;
PVR_ERROR GetDriveSpace(uint64_t& total, uint64_t& used) override;
PVR_ERROR CallSettingsMenuHook(const kodi::addon::PVRMenuhook& menuhook) override;