PullRequest: enhanced form

UI related changes:
* changed the right-arrow icon to more longer and bigger one, and set the position of it to vertically center.
* added rounded box around the project and branch information.
* added summary which shows the status of the pull-request and count of commits.
* removed unnecessary right-arrow icon in the commit list.

Functional changes:
* when a user click the new pull-request button, shows only branch information, title and content body.
* after then, the work checking the pull-request's status and diff commits is triggered by AJAX.
* when the AJAX response come, refresh(or add) commit lists and update summary information.
removed unnecessary code
PullRequest: enhanced the message for disabled accept button

There are many reasons why the pull-request is not acceptable.
However, current yobi is just using not-enough-review-point message for all the situation.
So, I fixed to show appropriate message for many cases:
- when the pull-request is not open(ex, clsoed, canceled or accepted)
- when it is on merging.
- when it is conflicted.
- when it doesn't have enough reviewrs.
modify the contents regarding feedbacks.
Merge branch 'spec/yobi-organization-plan' of changsung/yobi

from pull request 637
chagnes file name, korea to english.

Private-issue: 1511
Merge branch 'issue-1511' of changsung/yobi

from pull request 1043
Merge branch 'enhance/issue-1498' of whiteship/yobi

from pull request 1031
Merge branch 'pullrequest/reivew' of whiteship/yobi

from pull request 1012
Merge branch 'pullrequest/create' of whiteship/yobi

from pull request 1002