gtest genesis parsing

• only embed chainspec when feature enabled
• change existential deposit to match g1v1
• adapt genesis parsing to real-world data

# build with gtest feature
cargo build --release --features gtest --no-default-features
# run with custom genesis
DUNITER_GTEST_GENESIS=~/dev/py-g1-migrator/output/gtest_genesis.json duniter --tmp --alice --chain=gtest_dev

docs/dev/setup.md

@@ -35,7 +35,7 @@ Use a terminal shell to execute the following commands:
 ```bash
 sudo apt update
 # May prompt for location information
-sudo apt install -y cmake pkg-config libssl-dev git build-essential clang libclang-dev curl
+sudo apt install -y cmake pkg-config libssl-dev git build-essential clang libclang-dev curl protobuf-compiler
 ```
 
 ### Arch Linux