We'd like to live in a world where we can retry all the pending
conflicts in a conversation as a batch, which means we don't want to
wipe the identity key before processing each message. Thus, remove that
step from these handlers and encapsulate in a method on the conversation
model.
Ensure that both tryAgain functions return promises, allowing the
application to take appropriate action in the result of success or
failure. This lets us remove all dependency from libtextsecure on
app-level constructs like message objects/ids and the `extenion.trigger`
function.
Corresponding frontend changes to follow in another commit.
Let libaxolotl throw a generic error instead of a replayable error, and
add an helper function in libtextsecure's axolotl_wrapper to catch and
convert from the generic error to the replayable one. This allows the
ReplayableError to remain a libtextsecure-level concept only.
Somewhat unrelatedly, but nearby, fix some whitespace and add missing
semicolon.
