IPEX grant, admit, spurn support in KLI (WebOfTrust#572)

* IPEX protocol state machine.

Refactoring of Exchanger to inline calls to behaviours and allow for behaviours to verify a message against a given protocol before persisting the message.

* Full test coverage of the IPEX state machine.

* Remove final vestiges of signing credentials.  We are no longer signing credentials or processing, streaming or storing signatures on credentials.

* I no longer sign my credentials, and you shouldn't either.

Signed-off-by: pfeairheller <[email protected]>

* All tests and scripts updated to work

Signed-off-by: pfeairheller <[email protected]>

* Update challenge response handle to fix breaks from refactor.

Signed-off-by: pfeairheller <[email protected]>

* Implement IPEX grant, admit, spurn and list.

Signed-off-by: pfeairheller <[email protected]>

---------

Signed-off-by: pfeairheller <[email protected]>

scripts/demo/basic/challenge.sh

@@ -2,9 +2,11 @@
 
 kli init --name cha1 --nopasscode --config-dir "${KERI_SCRIPT_DIR}" --config-file demo-witness-oobis
 kli incept --name cha1 --alias cha1 --file ${KERI_DEMO_SCRIPT_DIR}/data/challenge-sample.json
+kli ends add --name cha1 --alias cha1 --eid BLskRTInXnMxWaGqcpSyMgo0nYbalW99cGZESrz3zapM --role mailbox
 
 kli init --name cha2 --nopasscode --config-dir "${KERI_SCRIPT_DIR}" --config-file pool2-witness-oobis
 kli incept --name cha2 --alias cha2 --file ${KERI_DEMO_SCRIPT_DIR}/data/challenge-sample-pool2.json
+kli ends add --name cha2 --alias cha2 --eid BLskRTInXnMxWaGqcpSyMgo0nYbalW99cGZESrz3zapM --role mailbox
 
 cha1_oobi="$(kli oobi generate --name cha1 --alias cha1 --role witness | sed -n '2 p')"
 cha2_oobi="$(kli oobi generate --name cha2 --alias cha2 --role witness | sed -n '2 p')"