Expose params in BarrageDescriptor class

[wongzigii]

/// 属性字典 @property(nonatomic,strong,readonly)NSMutableDictionary * params;

While I initializing a descriptor, I would like to modify the param before the render to receive. So is this possible to expose the params, eg: textColor or font family to interface file? At this time, I need to check out the demo to see which are the optional params before I getting start.

[unash]

这一点主要是考虑自定义 Sprite，其配置参数也可能自定义。此配置参数由 Descriptor 传过来，而 Descriptor 为统一接口对象，不方便为期添加便捷属性，故使用了字典来传递。

实在需要，只能由业务层自己创建一个转换器了。