VideoPress: Option to have video start from beginning upon browser refresh

### What

Option to have video start from beginning upon browser refresh

### Why

User expects video to start from beginning after a browser refresh, or have an option to control that.

Can test with video at https://jetpack.com/jetpack_support_tag/videopress/
Watch the video for a few seconds, then refresh the browser, the video will continue where it left off.

I checked the default behavior on main video services, and it defaults to starting from the beginning, you can test at:

* YouTube: https://www.youtube.com/watch?v=EIy-NN_0IN0
* Vimeo: https://vimeo.com/194343132

### How

Change the default behavior of VideoPress to start from beginning upon refresh, or add an option for that.

Ticket: 4555807-zd-woothemes

Start by reproducing the behavior on the VideoPress test page: watch for a few seconds, refresh, and confirm playback resumes at the previous position. Review the VideoPress browser playback entry point and determine whether done means restarting from the beginning by default or exposing an option that controls the refresh behavior.

Written by the indexing model from the issue text.