Add extra fields to resource table

[kindly]

add extra fields to resource as outlined in

​http://wiki.ckan.net/Domain_Model/Resource

Specifically (all unicode strings except for those noted):

• name: a name for this resource (could be used in a ckan url)
• type: the type of the resource. One of: file | api | service | listing
• mimetype: standard mimetype (e.g. for zipped csv would be application/zip)
• mimetype-inner: mimetype of innermost object (so for example would be text/csv)
• size: [integer] size of the resource (content length) in bytes. Usually only relevant for resources of type file.
• last_modified: [use datetime or just stick with iso formatted string?] the date when this resource's data was last modified (NB: not the date when the metadata was modified).
• cache_url: url for cache of object in ckan storage
• cache_last_updated: timestamp when cached version was created
• webstore_url:
• webstore_last_updated: timestamp when webstore was last updated