create one kind from two: ash_review

ash_review_request --- is not a valid kind for ash.
ash_review --- is more common one, because you can perform two actions on
review list: a) open in review mode; b) list files in review.

Allow you to use in ~/.vimrc:
```
    imap <silent><buffer><expr> <C-T> unite#do_action('split')
    call unite#custom#alias('ash_review', 'split', 'ls')
```