Prepare for sub to eth relay - part2 (#253)

* fixed PoA contract deploy (granda_authorities call)

* pause if all submitted headers were rejected

* give funds to Bertha and Carlos

* max 1 active PoA transaction in headers sync :(

* display initial header id when deploying PoA contract

* cargo fmt + clipy

* update PoA contract to accept <= 4 Substrate headers at once

* pause submitting headers when contract rejects all new headers + we have active transactions

* fix compilation

* cargo fmt --all

* does_not_select_new_headers_to_submit_when_submit_is_paused

* updated bridge contract

* Update relays/ethereum/src/sync.rs

Co-authored-by: Hernando Castano <HCastano@users.noreply.github.com>

* WiP.

* Submit first incomplete header.

* Finish up test.

* cargo fmt --all

* Remove redundant clone.

* Address review comments.

* cargo fmt --all

* Fix clippy.

Co-authored-by: Hernando Castano <HCastano@users.noreply.github.com>
Co-authored-by: Tomasz Drwięga <tomasz@parity.io>