shows user's avatar if he or she is a hive's user

If the commit email is one of the hive's user's one, then shows the user's
avatar, otherwise shows the email's gravatar.
changed gravatar's default image to hive's default image
assign user on issue's edit page
Merge pull request #22 from wansoon/HIVE-168

assign user on issue's edit page
refactoring
Merge pull request #23 from wansoon/HIVE-170

이슈 담당자 목록 처리 로직 리팩토링 & placeholder 메시지 변경
fixed a bug when adding a comment
conf: db logging enable
new feature: SignUp, pending to use and account locking

- new to hive sign-up user, pending to user until site admin confirm.
- site admin can lock user account at sites/settings menu
if you want to use sign-up confirm, uncomment below property in application.conf
#signup.require.confirm = true

see, HIVE-138
Merge pull request #24 from keesun/HIVE-160

댓글 입력할 때 발생하는 NPE 버그 수정
add active label on create new label
fix: broken tests
Merge pull request #26 from wansoon/HIVE-166

이슈 등록/수정에서 신규 라벨 추가시 Active 상태로 설정
Merge pull request #21 from keesun/HIVE-32

커밋 히스토리에 보이는 아바타 이미지 수정
Merge pull request #25 from doortts/HIVE-138

사용자 계정 잠금 기능
security: add some site admin feature auth check code
feature: add sorted view myproject list in front page
Merge pull request #27 from laziel/master

HIVE-36, HIVE-163, HIVE-171
fix CSS/JS for repository URL at project home (HIVE-173)
add JavaScript module for project home