When a user tried to reset password, yobi responded 200 OK even if the
url to reset password was wrong. It made users to think the password was
changed successfully but actaully it was not.

Respond 400 Bad Request with an error page.

from pull-request 1550

* enhance/watcher-count:
  project: add notification setting button at project watch/unwatch menu
  project: show project watcher count
  issue: fix wrong contextual message & key

Reviewed-by: 이응준 

from pull-request 1568

* enhance/git-i18n:
  git: Make git server supports i18n

Reviewed-by: 백기선 

from pull-request 1588

* fix/notification-for-updated-comment:
  notification: Add missed messages for comment update

Reviewed-by: Keesun Baik 

Make Yobi as a git server says in user's preferred language. Git
2.4.0-rc0 or more is required.

Yobi did not handle some cases correctly about config files.

* Fix a bug that the config files specified by user are ignored; In the
  case, do not create the files by default even if they don't exist.
* Do not update application.secret if the config file is out of conf
  directory. The file may not be Yobi's.
* Tell the user to update application.secret if Yobi failed to update
  it.
* Refactoring: Move members for config files into the ConfigFile inner
  class

Problem: When a user prefers "ko-KR" and Yobi has a "ko" message, Yobi
does not show "ko" messages for the user because PlayFramework thinks
"ko" does not match with "ko-KR".

Solution: Rename message files to have country code; e.g. messages.ko ->
messages.ko-KR.