Fix #218 and #158

Add the trait CheckAccountWorthiness defined in the pallet-identity and implemented in the duniter-account pallet, exposing the Fungible trait, that checks if an account exists and if this account has enough balance to pay for the entire identity creation process. This will change the identity creation process as follows:

1. Create the account by transferring at least twice the existential deposit.
2. Create the identity.

pallets/distance/src/mock.rs

@@ -233,6 +233,7 @@ impl pallet_identity::Config for Test {
     type AccountLinker = ();
     type AutorevocationPeriod = AutorevocationPeriod;
     type ChangeOwnerKeyPeriod = ChangeOwnerKeyPeriod;
+    type CheckAccountWorthiness = ();
     type CheckIdtyCallAllowed = ();
     type ConfirmPeriod = ConfirmPeriod;
     type DeletionPeriod = DeletionPeriod;