Save / load map functionality using Tango

[jubeira]

Ideally, the robot should be able to enter a mode where the map is built using tango_ros_node functionality. The user should be able to teleoperate the robot while the app builds the map. Then, the user should be able to stop at some point, saving the created map.

The app should also allow loading previously saved maps for navigation purposes. Then, the selected map would be published as a static map where the robot can navigate. The initial localization in this case should be automatic, because Tango should be able to localize wrt. the previously created ADF.