Improve error reporting during recipe evaluation

* Report invalid action usages from tasks;
* Implement backtrace cleaning in CLI;
* Extract error class declarations in a new errors file;
* Replace raise with fail keyword in task DSL class.

lib/producer/core/recipe.rb

@@ -1,8 +1,6 @@
 module Producer
   module Core
     class Recipe
-      RecipeEvaluationError = Class.new(StandardError)
-
       attr_reader :code, :filepath
 
       def self.from_file(filepath)