* signer/clef: make use of json-rpc notification

* signer: tidy up output of OnApprovedTx

* accounts/external, signer: implement remote signing of text, make accounts_sign take hexdata

* clef: added basic testscript

* signer, external, api: add clique signing test to debug rpc, fix clique signing in clef

* signer: fix clique interoperability between geth and clef

* clef: rename networkid switch to chainid

* clef: enable chainid flag

* clef, signer: minor changes from review

* clef: more tests for signer