Primary key renaming

Improved consistency for existing core translation key names.

See flarum/core#265
- Completely overhauled core en.yml
- Replaced existing key names in all core JS files to match
- Extracted a hardcoded string in IndexPage.js
- Combined two app.trans calls in DiscussionControls.js
- Removed hardcoded spaces from LogInModal.js and SignUpModal.js
- Added two new keys from DiscussionControls.js (soft delete)
- Created two new “reused keys” to YML to accommodate same

js/forum/src/components/ReplyComposer.js

@@ -24,9 +24,9 @@ export default class ReplyComposer extends ComposerBody {
   static initProps(props) {
     super.initProps(props);
 
-    props.placeholder = props.placeholder || app.trans('core.write_a_reply');
-    props.submitLabel = props.submitLabel || app.trans('core.post_reply');
-    props.confirmExit = props.confirmExit || app.trans('core.confirm_discard_reply');
+    props.placeholder = props.placeholder || app.trans('core.composer_reply_body_placeholder');
+    props.submitLabel = props.submitLabel || app.trans('core.composer_reply_submit_button');
+    props.confirmExit = props.confirmExit || app.trans('core.composer_reply_discard_confirmation');
   }
 
   headerItems() {
@@ -75,7 +75,7 @@ export default class ReplyComposer extends ComposerBody {
           let alert;
           const viewButton = Button.component({
             className: 'Button Button--link',
-            children: app.trans('core.view'),
+            children: app.trans('core.composer_reply_view_button'),
             onclick: () => {
               m.route(app.route.post(post));
               app.alerts.dismiss(alert);
@@ -84,7 +84,7 @@ export default class ReplyComposer extends ComposerBody {
           app.alerts.show(
             alert = new Alert({
               type: 'success',
-              message: app.trans('core.reply_posted'),
+              message: app.trans('core.composer_reply_posted_message'),
               controls: [viewButton]
             })
           );