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.

spec/producer/core/recipe/dsl_spec.rb

@@ -50,7 +50,7 @@ module Producer::Core
 
         it 'raises a RecipeEvaluationError on NameError' do
           dsl = Recipe::DSL.new { invalid_keyword }
-          expect { dsl.evaluate(env) }.to raise_error(Recipe::RecipeEvaluationError)
+          expect { dsl.evaluate(env) }.to raise_error(RecipeEvaluationError)
         end
       end
     end