[IMP] base_external_referentials : improve doc string, not finish yet
[IMP] base_external_referentials : improve doc string, not finish yet

BT-fgarbely/connector,anybox/connector,hugosantosred/connector,zhaohuaw/connector,brain-tec/connector,js-landoo/connector,open-synergy/connector,Antiun/connector,esousy/connector,esousy/connector,fevxie/connector,BT-jmichaud/connector,gurneyalex/connector,sylvain-garancher/connector,BT-fgarbely/connector,js-landoo/connector,maljac/connector,sylvain-garancher/connector,dvitme/connector,gurneyalex/connector,acsone/connector,open-synergy/connector,acsone/connector,guewen/connector,brain-tec/connector,mohamedhagag/connector,anybox/connector,Endika/connector,mohamedhagag/connector,zhaohuaw/connector,BT-ojossen/connector,MindAndGo/connector,fevxie/connector,MindAndGo/connector,BT-jmichaud/connector,maljac/connector,brain-tec/connector,hugosantosred/connector,dvitme/connector,BT-ojossen/connector,acsone/connector,guewen/connector,Antiun/connector,Endika/connector