WIP: navmesh station posts to a url, responder receives llsd and then has the llpathing library extract and render the navmesh (if desired).

Reviewed by Richard.

EXP-1423 FIX FUI resets floater contents after closing them (Inventory Panel), this is inconsistant for previous sidebar users and introduces extra difficulty in productivity of the viewer.
EXP-1430 FIX Minimizing voice settings floater corrupts layout throughout rest of session

* Made the avatar pickers and destinations guide properly stack and position
  themselves.

Reviewed by Richard.

EXP-1433 FIX Speak button can be toggled while editing Input/Output devices when voice is deactivated