Small (bug) fixes.
Simplify the checking for triggers, for the plugins, by making
MeidoBot do some of the work for them.
Also make sure that the user defined trigger prefix doesn't contain
any whitespace, which breaks this functionality (besides many plugins
already assuming trigger + prefix is just one word).
This goes with the previous commit.
* IrcComm.cs:
* IrcMessage.cs:
* MeidoBot.csproj: Move IrcComm and IrcMessage to their own files.

* MeidoBot.cs: Slightly change the help message to better jive with
  the Reply format.
* MeidoBot.cs: Rearrange the internal layout of MeidoBot.

* MeidoPlugins.cs: Allow prefixes to be longer than 1 character.