Easier to show remote tracking relationship in Log List

These changes make it eaiser show remote tracking relationship in Log List.

1: If a local branch has remote tracking branch, indicate that, currently a round rectangle. 
![LogDialog-HasTracking-g5ac5e70](https://f.cloud.github.com/assets/2804967/37209/d801d358-5408-11e2-9c4e-27fa9a610322.png)


2: Put remote tracking branch next to the corresponding local branch.
![LogDialog-HasTracking-gcd11a7a](https://f.cloud.github.com/assets/2804967/37210/dc52bf30-5408-11e2-9421-fb77845a3f47.png)


3: Simplify remote tracking branch name, can shorten the label width.
![LogDialog-HasTracking-g62db8ca](https://f.cloud.github.com/assets/2804967/37211/e71e02a8-5408-11e2-86bb-094f292e71b7.png)