access-control: refactoring.

Extract isProjectResourceAllowed from isAllowed, and etc.
posting: Remove unused log.
issue,posting: Show buttons correctly.

* Show Modify and Delete button iff user has corresponding permission.
* Show Create button even if the user is anonymous.
only manager and site manager can see the project settings menu
update proejct's overview page

- display histories(issues, posts, commits)
- display project's source url and type.
- display closed and opend issue count
- display readme.md without regarding character's case.
refactoring codes that pick up readme.md file name
issue,posting: refactoring.

Between controllers for issue and posting,
* Make them be similar to each other.
* Remove duplication
issue,posting: Fix access control.

* Add missed access control code for creating new issue.
* Replace "401 Unauthorized" with "403 Forbidden" for the error pages if
the user has no permission. The "401 Unauthorized" is not suitable even
if the user is anonymous because it MUST include WWW-Authenticate header
field but actually we didn't.
issue: Add tests for access control.
Merge pull request #13 from keesun/HIVE-48

update project overview page
user: handle not existed user page access
security: remove apache shiro code at login
project: Owner must be a manager of own project.

* Owner cannot leave own project.
* Owner's role cannot be changed.
Merge pull request #16 from npcode/fix/access-control-issue-posting

이슈 및 게시판의 access control 버그(혹은 잘못된 구현) 수정
refactoring string to enum
removed code for checking a user variable is null, as it can't be null
Merge pull request #15 from keesun/HIVE-109

프로젝트 설정 권한이 없는 유저에게는 프로젝트 설정 메뉴가 나타나지 않도록 처리
Merge pull request #17 from npcode/fix/owner-cannot-leave

project: Owner must be a manager of own project.
fixed a bug

NoHeadException error occurs when an overview page is loaded while there is no HEAD
Merge pull request #20 from keesun/HIVE-153

HEAD가 없을 떄 오버뷰 화면에서 에러나는 버그 수정