Major changes, see description

-Replaced the module pre.js with pro.js this module handles the
connection with the firebase server and calculates the trajectories.
-Added a new visualization "server.html" to display the trajectories in
a space-time plane. this visualization uses the spacetime.js module

-New server connection. Now we use transit.firebaseio.com

-Deleted Fig.js replaced with spacetime.js
-Deleted status.html replaced with server.html

-some cleaning of firebus.js and implemented a new color (black) to
display No Service