exampleWeightColumnName v.s. weightColumnName

[wschin]

In trainers like

        internal RandomizedPcaTrainer(IHostEnvironment env,
            string features,
            string weights = null,
            string featureColumnName,
            string exampleWeightColumnName = null,
            int rank = Options.Defaults.NumComponents,
            int oversampling = Options.Defaults.OversamplingParameters,
            bool center = Options.Defaults.IsCenteredZeroMean,
            bool ensureZeroMean = Options.Defaults.EnsureZeroMean,
            int? seed = null)

we have exampleWeightColumnName but it seems weightColumnName is clear enough under this context. Can we switch to weightColumnName?

[Ivanidzo4ka]

origin of current name: #2257

[Ivanidzo4ka]

actually #2177 (comment)

[wschin]

Now, I feel exampleWeightColumnName is actually a good name. There are too many places where Weight is included in a variable names. Having example can clarify those cases.