move modules used by @eval to separate package

The two modules Lambdabot.Plugin.Haskell.Check.ShowQ and
Lambdabot.Plugin.Haskell.Eval.Trusted are only used by @eval.
Moving them reduces the trusted codebase, and, more importantly,
reduces the time required for loading the package, since
lambdabot-haskell-plugins pulls in the ghc API.
implement IRC server authentication