Add the Like button

[blazern]

• BackendProduct and Product should use the "likes_count" and "liked_by_me" fields from the backend
• When a product is "liked by me", the Like button should be active, otherwise inactive
• When clicked, the button sends either the "like_product" or the "unlike_product" cmd
• On button press (not on cmd success, because of slow Internet the cmd can execute after too much of time), the local "liked by me" and the likes_count fields should change their state accordingly