Merge pull request #10 from jay3/v1.3beta

V1.3beta
Added altitude to graph / time to display

Added altitude graph to use real data and added elapsed time to the display

Signed-off-by: Nicholas Jackson <nic@thatlondon.com>
Fix initial display for graph

Signed-off-by: Nicholas Jackson <nic@thatlondon.com>
Better logs

Use TAG constant, starting with PF-
Add method loadPreferences()
Better gestion of saved GPS stats

* method loadGPSStats(), saveGPSStats(), resetGPSStats()
* can now reset stats if GPS is not started
Confusion between state and button
Bugfix: reset button displays START button on pebble if GPS is started

Attention: need to install a new watchface