make header and side-bar ui parts non-selectable

1. reformat related code file, use uniform tabs or spaces in each single line .

2. make header and side-bar ui parts non-selectable
![qq 20150101184909](https://cloud.githubusercontent.com/assets/10270327/5592025/0a3c64c8-91e7-11e4-9713-6999c6b0b5bc.jpg)
![qq 20150101184922](https://cloud.githubusercontent.com/assets/10270327/5592026/0a3c8d7c-91e7-11e4-96c5-3c31dd7ec36a.jpg)

3. align editor and previewer initial height