f:all white-listing / ordering

in addition of blacklisting, allow white-listing to enable ordering.

Note: this really should NOT be extracted out of the constraints closure, its there for backwards compatability somehow, but layout information shouldnt be maintained in the model.

spec:
1. check property: include=comma separated list of properties (ordered)
1a. additional feature, should allow inclusion of properties that are excluded by default
1b. for all properties specified, apply sort-order from the list, for all properties not specified, add after included properties
2. check except property and exclude properties
3. render

Optional:
In addition yet a third stricter property could be introduced "whiteList" that will only render the properties listed in the order supplied.

Start by tracing the constraints closure and the include, except, and render handling described in the issue. Verify how excluded properties are currently selected and ordered before deciding where the requested ordering and optional whiteList behavior belong. Done means include can add and order properties, except still excludes them, unspecified properties follow included ones, and rendering matches the specification.

Written by the indexing model from the issue text.