Display decimal precision correctly

[LanesGood]

Implement a default decimal precision of tenths (0.0) for cluster/summary values.

We may need to establish a configuration mechanism for columns that should not have any decimal precision.

Population (and others) will not display a decimal.

[hanbyul-here]

This seems to be a part of #38 ? I will close 38 and leave this one until we get the columns for integers.