cherry-pick improvements from encointer

[brenzi]

A non-exhaustive list of improvements that should be picked from encointer in reverse order (could be mixed with encointer-specific stuff, so this will require cleanup):

newer to older
*encointer@1c1e3d6

• encointer@503b9a3

• encointer@a8772b6

• encointer@c33ddbf

• encointer@69d90e7

• encointer@35ae50a

• encointer@7f2c6be

• encointer@518cefc

[brenzi]

started work on
#174

picked all relevant downstream commits and fixed merge issues.

builds, but is untested

[brenzi]

when I run demo_shielding_unshielding.sh, I'm getting

Sync chain relay: Enclave wants to send 1 extrinsics
[2020-09-09T07:40:37Z ERROR substrate_api_client::rpc::client] extrinsic error code 1002: Verification Error: Execution(ApiError("Could not convert parameter `tx` between node and runtime: Error decoding field Call :: SubstrateeRegistry.0"))
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: InvalidStringLength', /home/abrenzikofer/.cargo/git/checkouts/substrate-api-client-9327f54164a9792a/cce8441/src/lib.rs:424:25
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

update: was running against wrong substraTEE-node version

[brenzi]

all fixed. demo_shielding_unshielding.sh is a success