Backend support coloring of node group based on access

[starsep]

Figure out how it should work exactly and support it.

[Zaczero]

When an AED group is returned, it has an access property. Just like a normal AED node does.

[Zaczero]

Here's the group access decision priority for reference. If at least one access=yes is contained, it will be access=yes. The goal is to make each group quickly represent the most accessible AED.