IntercomLayer

Need to display Intercom equipment and cabling as an overlay on the general plot drawings.

I don't want to hardcode specific devices. Rather, I want to be able to place generic devices and be able to describe them in terms of function for design purposes and then identify the specific hardware that provides the required function.

Have created the Device class with various attributes.

• 'id' (required) is a unique name to identify the item. (The uniqueness is not currently enforced.)
• 'on' (required) is the place where it the device is put. It needs to be the id of something that can be stacked on.

The Table class has been augmented to allow for an optional 'id' attribute.

Created the abstract Stackable class to keep the set of references of things that can have other things placed on them. This is mostly just like the 'Mountable' class, except that items listed in it can have other items stacked on top of them rather than hung from them.

Tables will be Stackable. The Device 'on' attribute will be required to reference a Stackable thing.