Implemented outdoor navigation for google maps api V2.

NB: GPS not implemented. Single touch to set start position and clear all destinations, long touch to set destination.

+ micc.beaconav.map.navigation: new package for manage google directions request for outdoor navigation.
   + GMapRouteManager: interface for the package user
   + Navigation: represent a list of possible Routes
   + Route: navigation instruction for going from A to B passing by all waypoints C1, C2, ... Cn. (A -> C1 ->.. ->Cn -> B)
   + Leg: navigation instruction for going from a point to the next point (A to C1 or Ck to Ck+1 or Cn to B, or A to B if no waypoints ar setted)
   + Step: single line in a leg, represent the line (polyline) that join two consecutive street intersections, or two consecutive navigation directions (like "turn right" etc..)

+ Map use navigation package an GMapRouteManager to generate a request for routing/directions to google, download the response, converting the response in Navigation-Route-Step-Leg composition.

+ Map use Navigation-Route-Step-Leg composition to draw a single Route into the map!

TODO:
- Add launch separate thread to manage directions request/response (now UI is waiting response..)
- Add position localization (GPS)