Greatly simplify history management code (#2230)

Fixes #2220

This drops the ability to shift+click on “Back” to get back to a pinned
column, but that was inconsistent, broken, and undocumented.

This also brings us slightly closer to upstream.

app/javascript/flavours/glitch/features/account_timeline/components/moved_note.jsx

@@ -21,9 +21,7 @@ export default class MovedNote extends ImmutablePureComponent {
   handleAccountClick = e => {
     if (e.button === 0) {
       e.preventDefault();
-      let state = { ...this.context.router.history.location.state };
-      state.mastodonBackSteps = (state.mastodonBackSteps || 0) + 1;
-      this.context.router.history.push(`/@${this.props.to.get('acct')}`, state);
+      this.context.router.history.push(`/@${this.props.to.get('acct')}`);
     }
 
     e.stopPropagation();