Implement identicon representation for devices.

The first fifteen characters of device IDs are now used to procedurally
generate psuedo-unique avatars for their respective devices. The avatars
are represented using SVG elements that replace the icons previously
shown next to device names in the GUI.
Slight increase of contrast in identicons
Add cdata
Merge branch 'pr/871'

* pr/871:
  Slight increase of contrast in identicons
  Implement identicon representation for devices.

Conflicts:
	internal/auto/gui.files.go