Merge photos when combining sources

[thebnich]

CompositePlaceProvider sets fields from multiple places, but once a particular field has been set, it's ignored for others. For example, once we have photos from Yelp, TA/Wikipedia photos are dropped.

We can make this better by merging photos and categories from multiple sources. As part of this, we'll want to de-dupe any values.

[mcomella]

Merging categories sounds complicated:

• We have to filter our places on Yelp categories before we merge them
• As you mention, de-dupe (we have to handle plurals, e.g. Bar -> Bars, as well as potentially concatenation, Bar -> Bar & Restaurant)

Unless the Yelp category list is a problem from the user perspective, I think we should just keep it simple and use the Yelp categories.

[thebnich]

Fair enough; morphing this to be for photos only.