[Bug]: custom style property is not working when toRequire attribute is set

I managed to hotfix it by extending `isTargetStylable` method inside PropertyView.js - https://github.com/artf/grapesjs/blob/85b7b82103e12fb01a3700b1002a57a7b60ccaf1/src/style_manager/view/PropertyView.js#L504-510

I replaced this

> if (toRequire) {
      stylable =
        !target ||
        (stylableReq &&
          (stylableReq.indexOf(id) >= 0 || stylableReq.indexOf(property) >= 0));
    }

with this 

> if (toRequire) {
                        stylable =
                            !target || 
                             trg.cid === this.getTarget().cid || 
                            (stylableReq &&
                                (stylableReq.indexOf(id) >= 0 || stylableReq.indexOf(property) >= 0));
                    }

It seems that the wrong `target` parameter comes inside the method on component style change

JSFiddle with extended PropertyView - https://jsfiddle.net/6zf03t9w/

Offtop
I don't want to create another topic, just want to say that in the same method(isTargetStylable) that would be better to replace searching for property with id(as I understand for the built-in styles, it is the same as the property) inside unstylable(as well as stylable) check 

> if (_.isArray(unstylable)) {
          stylable = unstylable.indexOf(property) < 0;
        }

->

> if (_.isArray(unstylable)) {
          stylable = unstylable.indexOf(id) < 0;
        }

Since I had a problem with displaying a custom style for a component of the same property as the built-in one. (in my application, the built-in style should be displayed for some components, and custom for others)