[Feature request] Put label hints and key shortcut hints back to Annotation page

[kuraga]

Feature description

As mentioned in #509, #627, we have removed:

1. label buttons,
2. key shortcut hints,
3. annotation progress bar
   in v1 UI.

This proceed some disadvantages:

1. Annotators don't see key shortcuts.
2. Annotators have to do two additional mouse movements:
   a. open labels list,
   b. close labels list: because they don't see next document's text until.

So I propose to put label buttons and key shortcut hints back to Annotation page.

[icoxfog417]

duplicate to #834

[kuraga]

@icoxfog417 , no, #834 is only a subset of this. Moreover, ideas are totally different. This issue proposes to recover historical behavior (and explains, why). That issue proposes to make a little change which doesn't solve problems explained here.

[kuraga]

Fixed.