* Replace undefined error in currency adapter.

* Update tranact asset errors.

* Update TransactAsset trait documentations.

* Update currency adapter error documentation.

* Add Xcm sender.

* Rename XCM sender and add description.

* Update copyright header.

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>

* update tiny-keccak to 0.2

* update deps except bitvec and shared_memory

* fix some warning after futures upgrade

* remove useless package rename caused by bug in cargo-upgrade

* revert parity-util-mem *

* remove unused import

* cargo update

* remove all renames on parity-scale-codec

* remove the leftovers

* remove unused dep

Co-authored-by: Gavin Wood <gavin@parity.io>

Co-authored-by: Gavin Wood <gavin@parity.io>