PLT-1378 Initial version of emoji reactions (#4520)

* Refactored emoji.json to support multiple aliases and emoji categories

* Added custom category to emoji.jsx and stabilized all fields

* Removed conflicting aliases for :mattermost: and :ca:

* fixup after store changes

* Added emoji reactions

* Removed reactions for an emoji when that emoji is deleted

* Fixed incorrect test case

* Renamed ReactionList to ReactionListView

* Fixed 👍 and 👎 not showing up as possible reactions

* Removed text emoticons from emoji reaction autocomplete

* Changed emoji reactions to be sorted by the order that they were first created

* Set a maximum number of listeners for the ReactionStore

* Removed unused code from Textbox component

* Fixed reaction permissions

* Changed error code when trying to modify reactions for another user

* Fixed merge conflicts

* Properly applied theme colours to reactions

* Fixed ESLint and gofmt errors

* Fixed ReactionListContainer to properly update when its post prop changes

* Removed unnecessary escape characters from reaction regexes

* Shared reaction message pattern between CreatePost and CreateComment

* Removed an unnecessary select query when saving a reaction

* Changed reactions route to be under /reactions

* Fixed copyright dates on newly added files

* Removed debug code that prevented all unit tests from being ran

* Cleaned up unnecessary code for reactions

* Renamed ReactionStore.List to ReactionStore.GetForPost

webapp/utils/utils.jsx

@@ -539,6 +539,7 @@ export function applyTheme(theme) {
     if (theme.mentionColor) {
         changeCss('.sidebar--left .nav-pills__unread-indicator', 'color:' + theme.mentionColor);
         changeCss('.sidebar--left .badge', 'color:' + theme.mentionColor + '!important;');
+        changeCss('.app__body .post-reaction--current-user', 'background-color:' + changeOpacity(theme.mentionColor, 0.4));
     }
 
     if (theme.centerChannelBg) {
@@ -628,6 +629,8 @@ export function applyTheme(theme) {
         changeCss('.app__body .post.post--comment.current--user .post__body', 'border-color:' + changeOpacity(theme.centerChannelColor, 0.2));
         changeCss('.app__body .channel-header__info .status .offline--icon', 'fill:' + theme.centerChannelColor);
         changeCss('.app__body .navbar .status .offline--icon', 'fill:' + theme.centerChannelColor);
+        changeCss('.app__body .post-reaction:not(.post-reaction--current-user)', 'background-color:' + changeOpacity(theme.centerChannelColor, 0.2));
+        changeCss('.app__body .post-reaction', 'border-color:' + theme.centerChannelColor);
     }
 
     if (theme.newMessageSeparator) {