Auto-pin first message in help threads

[Zabuzard]

The bot should automatically pin the first message in help threads, this is usually the OPs question, or directly next to it.

Makes it easier for people to navigate in a help thread if they can just jump all the way up.

Implementation-wise, this could be added directly into the flow of AskCommand.java and ImplicitAskListener.java, where it also creates the threads and posts the first automatic messages.