66-67 Data migration is broken

067_turn_extras_to_strings.py is currently broken due to okfn/ckan@7677d69e , this is an example from a dump of pdeu before the change, after the change and what query should be executing.

	pdeu=# select count(id) from package_extra  where left(value,1) = '"';
	 count  
	--------
	 274194
	(1 row)

	pdeu=# select count(id) from package_extra  where substr(value,0,1) = '"';
	 count 
	-------
		 0
	(1 row)

	pdeu=# select count(id) from package_extra  where substr(value,1,1) = '"';
	 count  
	--------
	 274194
	(1 row)

substr counts from 1, see examples in [postgres docs](http://www.postgresql.org/docs/9.1/static/functions-string.html)