#49 red: changed Exec scenarios to use Task<T> syntax and added ExtensionMethod scenario
#49 green: added BauPack.Task<T> and changed ExecTask to Exec
#49 refactor: simplify plugins by moving script pack and action execution into Task
#49 refactor: simplify greeter sample plugin
#49 refactor: move greeter plugin to plugins folder
#49 refactor: add HelloWorld sample plugin
Merge pull request #51 from adamralph/49

#49 Remove requirement for plugins to provide extension method