* slash relayer balance for invalid transactions

* require some gap before unstake is possible

* more clippy

* log priority boost

* add issue ref to TODO

* fix typo

* is_message_delivery_call -> is_receive_messages_proof_call

* moved is_receive_messages_proof_call above

* only slash relayers for priority transactions

* Update primitives/relayers/src/registration.rs

Co-authored-by: Adrian Catangiu <adrian@parity.io>

* Update primitives/relayers/src/registration.rs

Co-authored-by: Adrian Catangiu <adrian@parity.io>

* Update bin/runtime-common/src/refund_relayer_extension.rs

Co-authored-by: Adrian Catangiu <adrian@parity.io>

* Update bin/runtime-common/src/refund_relayer_extension.rs

Co-authored-by: Adrian Catangiu <adrian@parity.io>

* Update bin/runtime-common/src/refund_relayer_extension.rs

Co-authored-by: Adrian Catangiu <adrian@parity.io>

* Update modules/relayers/src/lib.rs

Co-authored-by: Adrian Catangiu <adrian@parity.io>

* Update primitives/relayers/src/registration.rs

Co-authored-by: Adrian Catangiu <adrian@parity.io>

* benificiary -> beneficiary

---------

Co-authored-by: Adrian Catangiu <adrian@parity.io>