Better generic support for JSON in NewsItem attribute fields

[slinkp]

See for example openblock/ebdata/ebdata/scrapers/us/ma/boston/restaurants. This stuff JSON in a single Attribute column. Works OK for storage, but there's no way to index it, and no good general way to display it.
All we have is the eb_json.py template filter, which doesn't give us any useful way to use the lookup IDs that are stored in there by the restaurants scraper.

Two possible solutions:

• either eb_json.py could grow support for resolving Lookup IDs (how? look for dict keys with that magic name?) ...
• or the newsitem_detail view could grow a hook where you could somehow register type-specific code to enhance the context.

[slinkp]

(In [b32bdb2]) Hackish support for displaying the restaurant inspections JSON. refs #249

[slinkp]

Ticket imported from Trac:
http://developer.openblockproject.org/ticket/249
Reported by: slinkp