Add blueprint aiming tool to web UI

[brunchboy]

The OSC based aiming tool is a neat demo, but requires a network and phone or tablet running an OSC control surface. The web UI could have a similar feature built in.

To support this, add the ability to tie an image file of a plan or blueprint of the stage area (and possibly surrounding room) to a show, along with geometric information (location of show space origin on the plan, and orientation and scale).

When this information was configured, Aim cues running in the web UI would offer a map icon button which would open a new window showing the blueprint image and the current aim point, which could be dragged around the image to adjust the X and Z coordinates of the cue (and then possibly save it or use it in a new macro). There could be a slider on the side to set the Y coordinate as well, with marks showing floor and ceiling height.