PLT-3077 Add group messaging (#5489)

* Implement server changes for group messaging

* Majority of client-side implementation

* Some server updates

* Added new React multiselect component

* Fix style issues

* Add custom renderer for options

* Fix model test

* Update ENTER functionality for multiselect control

* Remove buttons from multiselect UI control

* Updating group messaging UI (#5524)

* Move filter controls up a component level

* Scroll with arrow keys

* Updating mobile layout for multiselect (#5534)

* Fix race condition when backspacing quickly

* Hidden or new GMs show up for regular messages

* Add overriding of number remaining text

* Add UI filtering for team if config setting set

* Add icon to channel switcher and class prop to status icon

* Minor updates per feedback

* Improving group messaging UI (#5563)

* UX changes per feedback

* Update email for group messages

* UI fixes for group messaging (#5587)

* Fix missing localization string

* Add maximum users message when adding members to GM

* Fix input clearing on Android

* Updating group messaging UI (#5603)

* Updating UI for group messaging (#5604)

webapp/package.json

@@ -29,7 +29,7 @@
     "react-dom": "15.4.2",
     "react-intl": "2.2.3",
     "react-router": "2.8.1",
-    "react-select": "1.0.0-rc.3",
+    "react-select": "1.0.0-rc.2",
     "superagent": "3.4.1",
     "twemoji": "2.2.3",
     "velocity-animate": "1.4.2",