Sometimes we just want to accept the user's wrong, but when it comes
to remote APIs etc. we probably want to let the client know it has
done something already (in this case multiple identical subscription
requests - which might indicate to it that it should refresh the sub
lists or something).
clientError and serverError exit after they're done so no need for
break or return. Also, $this->format is default.
We also got rid of the incredibly verbose version of $this->isPost()
which was spread all over the place.
Not all of this cleaning up is done yet.
* Mostly punctuation updates so that the same message is used consistently in all of StatusNet.
* Some cases of "Title Case" removed, because that does not appear to be used consistently.