Pullrequest: fixed to show edit button

* Fixed to show edit button always, even if the pull-request is not safe to merge
Refactoring : ProjectApp

Remove getProject method
Extract vaildation method
Strings in `Notification Setting` are modified.

Cause:
Some messages was omitted.

Solution:
These omitted are added.

Private-issue: 1443
Set "No milestone" as selected on new issue form
Fix layout for buttons' row below content body
Remove unused placeholder message
usermenu: add 'my issues' link at usermenu
PullRequest: fixed to show reviewer's name instead of null

added user.refresh() before using it.
PullRequest: added reset and clean after merge or attemptMerge

When a pull-request did merge or attemptMerge operation, it was possible that there remains untracked file.
Because of it, the pull-request's repository couldn't move to other branch.
This causes non-stop waiting status and pull-request form error.

So I've added git reset and git clean operation after attemptMerge or merge.
Merge branch 'projectapp' of kirav/yobi

from pull request 1005
Merge branch 'fix-issuecreate-form' of laziel/yobi

from pull request 1011
Merge branch 'pullrequest/actions' of whiteship/yobi

from pull request 997
Merge branch 'issue-1443' of changsung/yobi

from pull request 1001
Merge branch 'fix-actrow-height' of laziel/yobi

from pull request 1010
Merge branch 'pullrequest/reviewers' of whiteship/yobi

from pull request 1014
Header: fix style of site admin icon at header
Header: fix size of user avatar icon at header
Merge branch 'fix/subtle-ui-enhancement' of doortts/yobi

from pull request 1024
Comment: prevent from repeated form submit

Check whether form has marked as "on submit"
at submit event handler of comment form.
Submitting form will be ignored if the form has already marked.
changes a message, `Sympathy`, to `Agree`.

Private-issue: 1484