Adding "export" form to entity view

[shushu]

To include an export "form" in the best way, I thought we should learn from a similar example - the "add to cart" form in Commerce.

In Commerce they use hook_field_info_alter() to change the default_formatter of a given field to their formatter, and in this formatter they add the form.

http://drupalcontrib.org/api/drupal/contributions!commerce!modules!cart!commerce_cart.module/function/commerce_cart_field_info_alter/7

I think we might want to do it the same way - selecting one field in the biblio entity and change its formatter to include the export form.

@amitaibu do you think this is the right way ? Any other generic way to do so ?