[新增] AjaxDeleteFileActionTest 尚未完成
Merge branch 'story_7111' of github.com:ezScrum/ezScrum into story_7111
merge commit
Merge branch 'story_7111' of github.com:ezScrum/ezScrum into story_7111

Conflicts:
	java/ntut/csie/ezScrum/web/action/AjaxAttachFileAction.java
	java/ntut/csie/ezScrum/web/control/ProductBacklogHelper.java
	test/ntut/csie/ezScrum/issue/sql/service/internal/MantisAttachFileServiceTest.java
	test/ntut/csie/ezScrum/web/helper/ProductBacklogHelperTest.java