Advanced settlement structures

The advanced settlement items are unlocked by meeting specific criteria.
 * Picking up Fallout 4 magazines; such as Picket Fences and specific issues of the Wasteland Survival Guide.
 * The Cabot House quest line also unlocks a set of portrait paintings.
 * Being friendly to specific factions unlocks flags.

Misc
Issue #4 Wasteland Survival Guide offers a new decoration item, the lawn flamingo. Further checking needed for more available items from this Issue.