Add fully customized indicator support for remote dependency.

[Muyangmin]

Thanks for providing so many nice built-in indicator, but in my actual usage experience, maybe it's not easy to customize on remote dependency, e.g. to provide multi paint color, or another animator type.

So I added this Fully customize indicator on remote dependency feature. By using reflection mechanism, user can specify their own subclass name on XML files. By support (Context, AttributeSet) constructor of indicator classes, user can even define any custom properties in XML, just as use standard libraries. Sincerely hope you would accept this PR, best wishes for you ~

[HarlonWang]

First of all, you are very good, because you gave me a good way to achieve .

以下画风转变 :)

其实，我的想法是，是想直接在xml定义com.example.MyIndicator，然后不用通过反射来处理自定义，可惜我目前并没有找到如此优雅的方式，如果你有比较好的想法，欢迎互相交流。再次感谢你的PR，虽然我没有merged，但还是希望你能感受到我满满的诚意 :)