[client] Add a skeleton of "Users" page
[client] Add buttons & checkboxes to add/delete user (based on "Actions").

They don't work yet.
[client][users] Add a callback function for checkboxes (based on "Actions")
[client][users] Add some comments (same with "Actions" page)
[client][hatoholNoYesMsgBox] Fix a bug that an argument "yesCallback" isn't used
[client][users] Make the table sortable (based on "Actions" page)
[client][users] Add skeleton of callback functions for add/delete button
[client][users] Implement deleting users (based on "Actions" page).

BTW I just only copy & paste the code in "Actions" page and
replace "action" with "user" to implement it. We should unify
these codes later.
[client][users] Add a skeleton of user edit dialog.

It's based on HatoholAddActionDialog, but I named it
"HatoholUserEditDialog" instead of "HatoholAddUserDialog"
because it will be used for editing an existing user too.

I think HatoholAddUserDialog should also be renamed to
HatoholActionEditDialog.
[client][HatoholUserEditDialog] Add entries to enter username & password
[client][HatoholUserEditDialog] Shrink width of the dialog
[client][HatoholUserEditDialog] Add implementation of onAppendMainElement()
[client][HaotholUserEditDialog] Implement adding an user
[client][HatoholUserEditDialog] Rename a function

validateAddParameters ->
validateParameters

The word "Add" isn't suitable because this dialog will also be used
for editing an existing user.
[client][HaotholUserEditDialog] Fix a typo.
an ->
a
[hatohol-def-src-file-generator] Add predefined OperationPrivilege values
[client][HatoholUserEditDialog] Add user type selector
[client][HatoholUserEditDialog] Gettextize user type labels
[client][HatoholUserEditDialog] Replace magic numbers with variables
[client][users] Replace flags with user types