[BUGFIX beta] Make Component.sendAction behave the same as {{action}} helper.

Currently, the `{{action}}` handlebars helper allows multiple parameters to be specified and are passed properly to the action's function, but `Component.sendAction` only passes a single parameter.

`ActionHelper.registerAction` (source [here](https://github.com/emberjs/ember.js/blob/99fea760c73a3e0264330debf81737b41f6e200c/packages/ember-routing/lib/helpers/action.js#L80-85)) converts the provided parameters into an array and calls the action's function with those arguments.

`Component.sendAction` (source [here](https://github.com/emberjs/ember.js/blob/99fea760c73a3e0264330debf81737b41f6e200c/packages/ember-views/lib/views/component.js#L194-213)) only passes the first argument to `TargetActionSupport.triggerAction` (in the `actionContext` property).

Regarding the BUGFIX tag, I personally thought this was a bug, but I would be happy to change the commit message if you'd prefer.

Also, `ember-dev` currently is having issues with multi-branch testing.  This does cherry-pick properly into `beta`, but has a minor conflict in `stable`.

Resolves https://github.com/emberjs/website/issues/985.