Remove account creation tax

See discussion https://forum.duniter.org/t/faire-le-tri-dans-la-pallet-duniter-account/11922

The account creation tax can be removed as well as the possibility to create an identity for an inexistant account.

changed milestone to %runtime-800

added RN-runtime label

assigned to @HugoTrentesaux

Haha! Closing as duplicate of #187 (closed)

closed