Use right room dimensions in graphs

[marcomicera]

As @SelyBarguest pointed out in #83:

The chart dimensions are based on the boards and not the device room. In this example the room is bigger then the rectangle created by the boards.

We might wanna postpone this to debug our localization algorithm and solve this issue once we are sure that no device within the room is actually displayed outside.

[marcomicera]

Update: #89 must be done first.
Then, I'd go for setting the room dimensions in

1. Radar
2. Timeline

plus some hardcoded extra centimeters (e.g., +100cm should be enough) for debugging purposes (so we can see devices outside the room).

[marcomicera]

Solved in cd5dba9.