[client] Add a new view "IssueSendersView" to show the list of issue senders

It's copied from ActionsView and cut off needless codes.
ActionsView & IssueSendersView may be unified later.
[HatoholAddActionDialog] Divide makeMainDivHTML()
[HatoholAddActionDialog][ActionsView] Add "hatohol." prefix to action type constants
[HatoholAddActionDialog][ActionsView] Add "hatohol." prefix to trigger comparsion type constants

CMP_EQ    -> hatohol.CMP_EQ
CMP_EQ_GT -> hatohol.CMP_EQ_GT
[IssueSendersView] Add "hatohol." prefix to trigger comparsion type constants

CMP_EQ    -> hatohol.CMP_EQ
CMP_EQ_GT -> hatohol.CMP_EQ_GT
[HatoholAddActionDialog] Add a temporal implementation to add an IssueSender action
[IssueSendersView] Always show add/delete buttons

When the user doesn't have the privilege, we should hide whole of
this page.
[client] Add a skeleton of a dialog to edit issue tracking servers
[IssueTrackersEditor] Add a table to show issue tracking servers
[IssueTrackersEditor] Show list of issue tracking servers
[IssueTrackersEditor] Fix indent
[IssueTrackersEditor] Enable to delete issue tracking servers
[IssueTrackersEditor] Add a skeleton of a dialog to edit an issue tracking server
[IssueTrackersEditor] Use a singular form for a resource name of REST API

issue-trackers ->
issue-tracker
[IssueTrackersEditor] Add a callback function "Edit" button
[IssueTrackerEditor] Add entries to edit properties of a issue tracker server
[IssueTrackerEditor] Enable to post a issue tracking server
[hatohol-def-src-file-generator] Add issue tracker types
[IssueTrackerEditor] Use hatohol.ISSUE_TRACKER_REDMINE instead of a magic number
[IssueTrackerEditor] Add simple validation