Added Support For Loading Video Dialog

[thetutlage]

Since you did a very nice job by creating this complete activity which takes care of playing video and screen orientation.

I added the support of dialog which will be shown while we are busy loading and setting video.

Let me know if you got any questions for me.

[gradha]

Thanks for your pull request. This repo is not meant to be a tutorial (especially since it doesn't work for me) nor I'm interested cosmetic features to it. I won't merge the pull request but will leave it open so that other people can locate your repo with UI improvements and check that out instead.