PLT-3145 Custom Emojis (#3381)

* Reorganized Backstage code to use a view controller and separated it from integrations code

* Renamed InstalledIntegrations component to BackstageList

* Added EmojiList page

* Added AddEmoji page

* Added custom emoji to autocomplete and text formatter

* Moved system emoji to EmojiStore

* Stopped trying to get emoji before logging in

* Rerender posts when emojis change

* Fixed submit handler on backstage pages to properly support enter

* Removed debugging code

* Updated javascript driver

* Fixed unit tests

* Fixed backstage routes

* Added clientside validation to prevent users from creating an emoji with the same name as a system one

* Fixed AddEmoji page to properly redirect when an emoji is created successfully

* Fixed updating emoji list when an emoji is deleted

* Added type prop to BackstageList to properly support using a table for the list

* Added help text to EmojiList

* Fixed backstage on smaller screen sizes

* Disable custom emoji by default

* Improved restrictions on creating emojis

* Fixed non-admin users seeing the option to delete each other's emojis

* Fixing gofmt

* Fixed emoji unit tests

* Fixed trying to get emoji from the server when it's disabled

webapp/package.json

@@ -18,7 +18,7 @@
     "keymirror": "0.1.1",
     "marked": "mattermost/marked#12d2be4cdf54d4ec95fead934e18840b6a2c1a7b",
     "match-at": "0.1.0",
-    "mattermost": "mattermost/mattermost-javascript#release-3.1",
+    "mattermost": "mattermost/mattermost-javascript#8e4c320d5af653eacb248455d77057a76ec28830",
     "object-assign": "4.1.0",
     "perfect-scrollbar": "0.6.11",
     "react": "15.0.2",