[GSoC 2018 - TrackGit] Progress Report 6

This is the sixth progress report for TrackGit project. I did the following in last week.

My mentor Stephen had put up few comments on my commits so far. I addressed them earlier this week. You can have a look at the comments thread here and here.

Made clone process threaded

The initial implementation of clone was blocking the UI thread. I used the pthread library to make the clone processes threaded. Now the clone command does not block UI.

Implemented Clone progress Window

In addition to making clone progresses threaded, I also implemented the displaying of clone progress. Unfortunately, the progress text is not displayed correctly, which should be solved soon.