add features and refac data

Petite refacto destinée à suivre le progrès des transactions et obtenir les messages d'erreur.

Intègre le commit de la branche origin/flodef-addCommands de @flodef.

Basé sur la MR !4 (merged).

doc/example.md

+# Examples of gcli commands for copy-paste
+
+Useful when developing: replace `gcli` by `cargo run --` to build in debug mode and launch gcli.
+
+## Mnemonics
+
+Used in duniter-indexer genesis config:  
+`pipe paddle ketchup filter life ice feel embody glide quantum ride usage`
+
+with derivations:
+
+- `//2` → `test1`
+- `//4` → `test2`
+- `//6` → `test3`
+
+Used in substrate for Alice, Bob and Co:  
+`bottom drive obey lake curtain smoke basket hold race lonely fit walk`
+
+with derivations:
+
+- `//Alice`
+- `//Bob`
+- `//Charlie`
+- ...
+
+## Commands
+
+```sh
+# get balance of test1 account
+gcli --address 5FeggKqw2AbnGZF9Y9WPM2QTgzENS3Hit94Ewgmzdg5a3LNa get-balance
+# get information about test1 identity (needs indexer)
+gcli identity --username test1
+# show address of given secret
+gcli --secret "pipe paddle ketchup filter life ice feel embody glide quantum ride usage"//2 show-address
+```
+
+## Indexer commands
+
+These commands uniquely relate with indexer
+
+```sh
+# show latest indexer indexed block
+gcli indexer latest-block
+```
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