Make street view window slugs unique

[mvollrath]

Overview:
The window positioning interface relies on being given a unique window slug for positioning windows. The slug is generated from the configuration of the instance being managed for ease of debugging, but it is not guaranteed to be unique, so identical configurations on the same machine will have overlapping windows with their launchers racing to apply their rules first (or last?)

Requirements:

• Street View window slugs are unique even when launcher instances have the same fov, yaw and pitch.

Development notes
Here is where the slug is generated.

The Python uuid library seems like an easy way to generate a unique name.

Testing scenario

• Configure a system with two lg_sv launchers with identical yaw, pitch and fov and launch Street View.
• Confirm that they have different window names with $ DISPLAY=:0 xwininfo -root -tree

[FuriousJulius]

PR here #393