add treasuries pallet

[brenzi]

• adds treasuries pallet and bumps democracy to add SpendNative proposals
• adds cli tooling for the above
• adds rpc

testing

./target/release/encointer-node-notee --dev --enable-offchain-indexing true

./bootstrap_demo_community.py --signer //Bob
nctr-dev next-phase
nctr-dev next-phase
nctr-dev next-phase
### fill treasury 
nctr-dev get-treasury --cid sqm1v79dF6b
# 5CWoc3mGF9VEnuZzBbPWxhKPvY743AGwxUbvkYQHS8yWZbem
nctr-dev transfer //Alice 5CWoc3mGF9VEnuZzBbPWxhKPvY743AGwxUbvkYQHS8yWZbem 1000000000000
nctr-dev balance 5CWoc3mGF9VEnuZzBbPWxhKPvY743AGwxUbvkYQHS8yWZbem
# 1000000000000
nctr-dev submit-spend-native-proposal //Alice //Bob 123456789012 --cid sqm1v79dF6b
nctr-dev list-proposals
# verify electorate is 3
nctr-dev vote //Alice 1 aye sqm1v79dF6b_1
# await confirming 
nctr-dev update-proposal-state //Alice 1
nctr-dev list-proposals
# verify approval
nctr-dev next-phase
# verify enactment
# should see
# encointerDemocracy.ProposalEnacted
# encointerTreasuries.SpentNative
# balances.transfer to Bob
nctr-dev balance 5CWoc3mGF9VEnuZzBbPWxhKPvY743AGwxUbvkYQHS8yWZbem
# treasury balance went down

[clangenb]

Two tiny remarks, looks good otherwise