quest: refactor javascript.

Add some helper function to make code more clean, and add some comment.
Something rely on css class to switch to id, almost everything had done,
but the display of question answering state hadn't.
quest: add answering status interface.
quest-layout: modify comment to make interface more clear.
quest-layout: fix QuestionTag syntax error.
quest-layout: implement answering color in horizontal layout.
quest-layout: implements button status for vertical layout.

Also remove some unneeded tags.
update quest.js structure for update button status
update button callback function in quest.js

but still has some bugs
quest-layout: fix the option word not aligned.
Merge branch 'master' of github.com:Ezgo-WordTest/Frontend
Merge branch 'master' into gh-pages