[usecase-webapi] Improve Jsenhance usecase

- Use green pass/red fail instead of green/red rectangle to indicate pass or fail.
- remove style.css file

Impacted TCs num(approved): New 0, Update 1, Delete 0
Unit test Platform: [Tizen-IVI]
Test result summary: Pass 1, Fail 0, Blocked 0
Merge pull request #574 from zhangjingx/zhangjingx/misc/jsenhance

[usecase-webapi] Improve Jsenhance usecase