Add condition to logger

[jbicker]

Sometimes (especially while development) it is useful to only log under certain conditions. This small enhancement enables to write such conditional logs like this instead of if blocks and console.log:
this.logger.condition(edge.id === 'edge1').log(this, 'Edge Bounds are: ', edge.bounds);

[spoenemann]

I'm not sure about that – a plain old if block still has advantages:

logger.condition(bla).log(expression that is expensive to compute);

vs.

if (bla) {
    logger.log(expression that is expensive to compute);
}

In the first case the "expression that is expensive to compute" is always evaluated. In the second case, it's only evaluated when the condition is met.

I'm afraid that the proposed API can lead to bad practices.