um.controller.Chat: reload backend using `App.backend.req`

common interface: a5245f8ce780b0afc2b630026cabbaf1a3d08cae
um.ctl.Chat destroyChat(): use `unlisten()` from `Ext.app.EventBusView`
cfg.modelChatUser: use CRUD model's ID === _id as id

* thus there's no need in extra config for disabling of
  saving items to backend

* this field will have 'statuser_id'
  4 chars status prefix:^^^^ hardcoded everywhere
um: make status names 4 chars wide; move status l10n here

* userman.css: add padding for `model.chatUser._id`
UI events: rename with namespace (e.g. 'initwes@UI' || 'wes4UI'); cleanup

'backendWaitEvents' -> 'initwes@UI' -- internal UI event (one of)
'backendEvents'     -> 'wes4UI'     -- event from backend for UI
              (entry point for all listeners of events like 'usts@um')

* ctl.Main.js: remove dummy
um.Chat: handle user status changes (using dummy data)