Add upload time remaining to Insight

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 2013-04-16 at 16 17 23](https://f.cloud.github.com/assets/1692189/386529/f2e2948a-a6a8-11e2-8930-598e4c886c4d.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.