expose shard and shard vault rpc call

[brenzi]

• add rpc method author_getShard
• add rpc method author_getShardVault

merge first: #1497

testing

run worker and wait until event ProxyAdded

cargo install websocat
echo '{"jsonrpc":"2.0","method":"author_getShard","params":[],"id":1}' | websocat wss://127.0.0.1:2000 --insecure
# yields: {"jsonrpc":"2.0","result":"0x80a173624009fb6aded0457c70389f6999161234d25d473bf40d603262f9cb32430000","id":1}
# correct shard (ignore first byte above): BsEgkWdZW7oeG8VPvPWbDWgpKdybWHUucNnDGaaobqkv 
#0xa173624009fb6aded0457c70389f6999161234d25d473bf40d603262f9cb3243 

echo '{"jsonrpc":"2.0","method":"author_getShardVault","params":[],"id":1}' | websocat wss://127.0.0.1:2000 --insecure
# yields: {"jsonrpc":"2.0","result":"0x8086bde27ebc5be7df6013e82a8d09a4bf7157ecfd176dc0b6e06094d1cbe307ad0000","id":1}
# correct accountid (ignore first byte above: 2MHFBhKVz66RBJSo1awcE9XXCZpMagYGMcraDp1WaMDLtew4
# 0x86bde27ebc5be7df6013e82a8d09a4bf7157ecfd176dc0b6e06094d1cbe307ad

qed.

[clangenb]

LGTM