meta_query support for BuddyPress content types

[boonebgorges]

It should be fairly easy to extend WP_Meta_Query so that we can use it for our own content types, and then to accept a meta_query argument in our main database query methods. At the moment, WP_Meta_Query::get_sql() doesn't give an easy way to override the meta table name, so we'd have to write our own version of that method, but we could pass a ticket upstream to WP to get around this down the line.

[tw2113]

Feels like this one can be marked as closed, since content type conversion doesn't appear to have occurred.

[r-a-y]

We actually do allow meta queries for all our components that have a meta table now.

Closing as worksforme.