Transition payload hash option names to hmac

The payload-hash-* options are imprecisely named. Clarify their function
as HMAC validations by renaming them. The existing options will continue
to work but are deprecated.  Log a warning if the old options are used.

All tests, examples, and documentation are updated.

Fixes #289

hooks.yaml.example

@@ -15,7 +15,7 @@
   trigger-rule:
     and:
     - match:
-        type: payload-hash-sha1
+        type: payload-hmac-sha1
         secret: mysecret
         parameter:
           source: header