Add upload time remaining to Insight (see #10689)

This PR adds displaying of upload remaining time to Insight uploader. It uses a rough estimate, but fares well with most tested images.

![Screen shot 2013-04-17 at 09 22 41](https://f.cloud.github.com/assets/1692189/390256/54b84422-a738-11e2-8548-a13549d3a2ca.png)


To test, please make sure it returns sane values on Windows, Linux and OS X (due to different OS API calls used to obtain the current time). This might not work with multi-file images.