Use logic functions instead of as_dict when indexing entities

[amercader]

The current search implementation uses the output of the the as_dict method of the domain Package object to update the index

​https://bitbucket.org/okfn/ckan/src/56c79e3fc44c/ckan/lib/search/index.py#cl-48

It also uses package_to_api1 in the SynchronousSearch? plugin:

​https://bitbucket.org/okfn/ckan/src/f9dfb0506594/ckan/lib/search/__init__.py#cl-93

This prevents extensions from being able to index custom properties (e.g. faceting by custom extras not included in the model).

The search should use the logic function to get the package properties:

get_action('package_show')(context,data_dict)