CHERRY-PICK #4200: Add documentation to SubmitSignedTransaction and actually make it work

Squashed commit of the following:

commit dc8d71c3
Author: Tomasz Drwięga <[email protected]>
Date:   Tue Dec 3 16:29:33 2019 +0100

    Split the method to avoid confusing type error message.

commit 0c4c0378
Author: Tomasz Drwięga <[email protected]>
Date:   Tue Dec 3 16:19:55 2019 +0100

    Make accounts optional, fix logic.

commit d715f645
Author: Tomasz Drwięga <[email protected]>
Date:   Tue Dec 3 10:06:20 2019 +0100

    Remove warning.

commit 3f38218a
Merge: f85b8903 368318c9
Author: Tomasz Drwięga <[email protected]>
Date:   Tue Dec 3 07:08:05 2019 +0100

    Merge branch 'master' into td-signed-transactions

commit f85b8903
Merge: f8c95403 d8d5da2c
Author: Tomasz Drwięga <[email protected]>
Date:   Mon Dec 2 13:57:25 2019 +0100

    Merge branch 'master' into td-signed-transactions

commit f8c95403
Author: Tomasz Drwięga <[email protected]>
Date:   Mon Nov 25 17:34:52 2019 +0100

    Forgotten import.

commit a645b90d
Author: Tomasz Drwięga <[email protected]>
Date:   Mon Nov 25 17:32:10 2019 +0100

    Fix naming and bounds.

commit bc28c605
Author: Tomasz Drwięga <[email protected]>
Date:   Mon Nov 25 17:01:05 2019 +0100

    Add documentation to signed transactions and actually make them work.