This Fixes #1134, #931 : Changing checkbox style

fixing settings checkbox pile-up issue as well as custom checkbox style

1 > Switched off default checkbox style in edit.css
2> Created custom checkbox style in edit.css
3> Fixed checkbox pile-up isue in settings panel
4> Applied same style for file upload checkbox
Screenshot attached after testing :
![seetings-check-box](https://cloud.githubusercontent.com/assets/6388509/5416472/e6fd148a-8255-11e4-97e9-2f8436ba2bf5.PNG)

Going forward this style will be applied to any new  checkbox added.

@gordonwoodhull 
Please review and let me know if this is fine.