Also, they die if the get too small.

Every Bot now has 3 additional counters:
1. Food consumed from natural sources (static food)
2. Consumed remains of Bots killed by other Bots
3. Consumed remains of Bots killed by the counting Bot itself

Temporarily, these counters are printed when a Bot object is destroyed.

The new vector type is called Vector2D and is an appropriate typedef
from Eigen::Matrix (defined in src/types.h).

Using the new classes GlobalView and LocalView, it is possible to
quickly build lists of objects surrounding a point. This is now used to
speed up the food range checks.

Needs more smoothness...

Exception is the colormap, which is completely non-implemented so far.

100% untested!