Uncheck "current object media only"

(Moved from https://github.com/artsmia/griot/issues/64)

> After working with the admins in the ArtStories WP media drawer, I think it would help to have the default for "Current object media only" be unchecked. Otherwise the search comes up null at first.

---

> Maybe when a search term is entered the 'current' checkbox should automatically uncheck

---

> Only the first time? Because otherwise you wouldn't be able to search
within current object media only if that continued to uncheck.

---

> Hmm, you're right. Right now it's checked all the time, even when there isn't an object associated.

> Would "don't limit media drawer to current object unless there is actually a current object" fix some confusion? If there is, it still defaults to checked.

> Then we could search the set of images associated with that object first. If there aren't any results it opens up to the full set of images?

---

> Yep, that's a great solution. Thanks!