Minor changes to the meidoComm variable/field. Also fix the logic in
OnMessage, we want to call the appropriate delegates for Channel and
Query messages whether the message begins with the prefix or not.
* IrcCalc.cs:
* MiscUtils.cs:
* UrlTitling.cs:
* RandomChoice.cs: Now uses the new capabilities of IrcMessage.

* IrcMessage.cs:
* MeidoCommon.cs: Add the ReturnTo property, which contains the proper
  target to return the message to. This depends on whether or not the
  message was a channel or a query message.
Make it use the new capabilities of IrcMessage.
Revert to only accepting trigger when encountered in a channel
message. Remove the string.Format's, instead use the overload of the
respective IrcComm method.
Possible future enhancements.
Rearrange case statements, so most common case is first.
Let's just rearrange them all.
Make it use the new IrcMessage/IrcComm capabilities and some small
changes.