Allow Homebox authors to edit only their own blocks

A good addition would be to allow blocks to only be editable (draggable, color changeable etc) by the Homebox "author". In other words similar to when a user creates a node and is its author and is the only one permitted to edit their particular node; other users can still view that node but cannot edit it since they're not the author.

Currently any Homebox attached to a user profile can only be viewed by the one user, which seams a shame. Similarly it would be better to only deny editing access as oppose to denying access to the entire Homebox page.