Affects Version/s: None
Fix Version/s: 2.1
Removed the HasDensity<P>-interface and replaced it with a "public double density(double x)"-method on the AbstractContinuousDistribution-class (it throws an exception as default if the classes don't override the method).
Implemented density-functions for the F-distribution, t-distribution, Weibull distribution, and Cauchy distribution (the only continuous ones without a density implemented).
A side-effect is that ChiSquaredDistributionImpl now uses an internal GammaDistributionImpl instead of a GammaDistribution. This is the only "major" change.
This improvement replaces https://issues.apache.org/jira/browse/MATH-330 (density implementation for the F-distribution) and https://issues.apache.org/jira/browse/MATH-331 (density implementation for the other three distributions).