Allow placement of child drawings

[DanSheps]

Use case

Currently, we have our datacenter racks laid out in locations by:

• Floor
• Room
• Row
• (Optional) Functional Group

Unfortunately, you cannot include devices in nested locations within the "Room" plan (Rack in Row 1, Infrastructure for example cannot be included in the "Room drawing").

You also cannot include child drawings (example, you lay out your row in a sub drawing)

Proposal

Allow placement of child drawings onto a parent locations drawing.

[jeffgdotorg]

Resolving as dupe of #6

[jeffgdotorg]

It's a sub-task of #6, not a duplicate. My bad.