Updated visual-studio-2012.css for cleaner view

* Changed selected file background for easy find close icon (look at the left side of file name)

before: 
![bvs_before_1](https://cloud.githubusercontent.com/assets/946095/4077327/0dc3d24e-2ec2-11e4-8d75-ac688754fc5e.png)
after:
![bvs_after_1](https://cloud.githubusercontent.com/assets/946095/4077328/0dc87452-2ec2-11e4-8eaa-bef7d9937921.png)

* Made the file extensions less visible

before:
![bvs_before_2](https://cloud.githubusercontent.com/assets/946095/4077329/0dd1c296-2ec2-11e4-83b2-2f49efc3c894.png)
after:
![bvs_after_2](https://cloud.githubusercontent.com/assets/946095/4077326/0dc37d12-2ec2-11e4-8ccc-a2a807b01122.png)

* Changed background (made readable) for change language button

before:
![bvs_before_3](https://cloud.githubusercontent.com/assets/946095/4077330/0dd72894-2ec2-11e4-8e87-e93d6876d30c.png)
after:
![bvs_after_3](https://cloud.githubusercontent.com/assets/946095/4077331/0dda4ef2-2ec2-11e4-93aa-7a86b4aa0dbe.png)