PLT-2784 Channel Navigation Shortcuts (#2979)

* Completed shortcuts

* Fixed up logic

* Removed shortcut conflicts

* Added code to limit channel navigation within group

* Made code conform to user display, fixed minor logic

* Completed shortcuts

* Fixed up logic

* Removed shortcut conflicts

* Added code to limit channel navigation within group

* Made code conform to user display, fixed minor logic

webapp/components/create_post.jsx

@@ -351,7 +351,7 @@ class CreatePost extends React.Component {
             return;
         }
 
-        if (!e.ctrlKey && !e.metaKey && e.keyCode === KeyCodes.UP && this.state.messageText === '') {
+        if (!e.ctrlKey && !e.metaKey && !e.altKey && !e.shiftKey && e.keyCode === KeyCodes.UP && this.state.messageText === '') {
             e.preventDefault();
 
             const channelId = ChannelStore.getCurrentId();
@@ -373,7 +373,7 @@ class CreatePost extends React.Component {
             });
         }
 
-        if ((e.ctrlKey || e.metaKey) && e.keyCode === KeyCodes.UP) {
+        if ((e.ctrlKey || e.metaKey) && !e.altKey && !e.shiftKey && e.keyCode === KeyCodes.UP) {
             const channelId = ChannelStore.getCurrentId();
             const lastPost = PostStore.getCurrentUsersLatestPost(channelId);
             if (!lastPost) {