Added Command class
Added ParameterException
Started rewriting CommandExecutor
Converted List of commands to a Dictionary for easier lookup.
Added ParameterException throwing in callbacks.
CommandExecutor.Execute now requires a ChatOutput in order to output any exceptions
Changed MainForm to work with the new CommandExecutor
Added help command and renamed ParameterException to CommandException
CommandReturn is no longer necessary
Merge pull request #2 from Express50/commandexecutor-rewrite

CommandExecutor Rewrite