Access params in operations using accessors instead of the 'params' object.

[mpantel]

Setting param_accessor_style :accessors for Hyperstack components enables accessing component parameters directly without the need to prepend the 'params' object. This isn't supported for operations and it would be a great syntactic sugar, if you could also access operations' parameters using an accessor of the same name. This call convention will also align the use of params across components and operations.