Allow user to sync meta data from Widen

[josephfusco]

Currently once an asset is added there is no way to automatically update the asset's metadata within WordPress with any changes from Widen.

This should be a button somewhere within wp-admin to initiate this action

We can also create a widen-media WP-CLI command to allow for metadata syncs programatically.

[josephfusco]

This has been completed for collections in #19 however general assets still need support.